Anthropic has been ordered by the US government to cut off its newest Claude Fable 5 and Mythos 5 models for fear of abuse by adversaries.

Reuters reports that Anthropic said it will “abruptly ​disable” its most advanced AI models for all users after the US government ordered it to suspend access to the models for foreign nationals, citing national security ‌concerns.

Officials reportedly believe a jailbreak could turn Fable 5 and Mythos 5 into vulnerability-discovery tools for adversaries, so Anthropic says it is disabling them worldwide rather than try to nationality‑filter access, since it is virtually impossible to verify every user’s nationality.

In a statement on its website, Anthropic says:

“The letter did not provide specific details of its national security concern. Our understanding is that the government believes it has become aware of a method of bypassing, or “jailbreaking” Fable 5. We reviewed a demonstration of this specific technique being used to identify a small number of previously known, minor vulnerabilities. These vulnerabilities all appear relatively simple, and we have found that other publicly-available models are able to discover them as well without requiring a bypass.”

Mythos 5 is the non-public full version, which is currently used only by government agencies and selected corporate partners to harden their systems. Fable 5 is a Mythos-class model that should supposedly be safe for general use.

It makes sense to me that if Fable 5 is easy to jailbreak, that it should fall under the same restrictions as Mythos 5. However, Anthropic maintains that it has built-in safeguards that mean queries on some topics will instead receive a response from the next-most-capable model, Claude Opus 4.8. 

The relationship between the US government and Anthropic had shown signs of easing in parts of the US government after tensions over military use, surveillance, and autonomous weapons. In March, defense Secretary Pete Hegseth designated the San Francisco-based company a “supply-chain risk to national security.”

To understand the nature of the argument, it is necessary to understand that Mythos 5 is described in multiple reports as particularly effective at identifying software vulnerabilities, including long‑standing bugs in complex, legacy systems such as those in banking and other critical infrastructure. Many view this as dual‑use: great for defense hardening, but catastrophic in the wrong hands.

In recent updates from major software vendors like Microsoft and Google, we’ve seen a growth in numbers of patched vulnerabilities after the vendors began using AI-guided search for new vulnerabilities in their own software. We also know that Mozilla found over 270 Firefox vulnerabilities with the aid of Anthropic’s new Claude Mythos model. 

What this means

In the wrong hands these vulnerabilities could definitely do a lot of harm. So, it looks like it will take some time before regular consumers and developers will gain access to Fable 5 and Mythos 5 entirely. However, existing Anthropic models (older Claude variants) remain available.

For home users who were simply chatting with Claude or using it to help with basic scripting, the change will mostly show up as “this specific version is unavailable” rather than a broader AI blackout.

Removing a high‑end vulnerability‑finding model from broad circulation increases the effort required for less‑resourced cybercriminals to automate discovery of complex bugs in consumer‑facing software and services only by so much. There are other models available on the black market that might be just as effective. And for most cybercriminals, turning a vulnerability into a method they can utilize in an exploit is much more relevant.

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

Anthropic has been ordered by the US government to cut off its newest Claude Fable 5 and Mythos 5 models for fear of abuse by adversaries.

Reuters reports that Anthropic said it will “abruptly ​disable” its most advanced AI models for all users after the US government ordered it to suspend access to the models for foreign nationals, citing national security ‌concerns.

Officials reportedly believe a jailbreak could turn Fable 5 and Mythos 5 into vulnerability-discovery tools for adversaries, so Anthropic says it is disabling them worldwide rather than try to nationality‑filter access, since it is virtually impossible to verify every user’s nationality.

In a statement on its website, Anthropic says:

“The letter did not provide specific details of its national security concern. Our understanding is that the government believes it has become aware of a method of bypassing, or “jailbreaking” Fable 5. We reviewed a demonstration of this specific technique being used to identify a small number of previously known, minor vulnerabilities. These vulnerabilities all appear relatively simple, and we have found that other publicly-available models are able to discover them as well without requiring a bypass.”

Mythos 5 is the non-public full version, which is currently used only by government agencies and selected corporate partners to harden their systems. Fable 5 is a Mythos-class model that should supposedly be safe for general use.

It makes sense to me that if Fable 5 is easy to jailbreak, that it should fall under the same restrictions as Mythos 5. However, Anthropic maintains that it has built-in safeguards that mean queries on some topics will instead receive a response from the next-most-capable model, Claude Opus 4.8. 

The relationship between the US government and Anthropic had shown signs of easing in parts of the US government after tensions over military use, surveillance, and autonomous weapons. In March, defense Secretary Pete Hegseth designated the San Francisco-based company a “supply-chain risk to national security.”

To understand the nature of the argument, it is necessary to understand that Mythos 5 is described in multiple reports as particularly effective at identifying software vulnerabilities, including long‑standing bugs in complex, legacy systems such as those in banking and other critical infrastructure. Many view this as dual‑use: great for defense hardening, but catastrophic in the wrong hands.

In recent updates from major software vendors like Microsoft and Google, we’ve seen a growth in numbers of patched vulnerabilities after the vendors began using AI-guided search for new vulnerabilities in their own software. We also know that Mozilla found over 270 Firefox vulnerabilities with the aid of Anthropic’s new Claude Mythos model. 

What this means

In the wrong hands these vulnerabilities could definitely do a lot of harm. So, it looks like it will take some time before regular consumers and developers will gain access to Fable 5 and Mythos 5 entirely. However, existing Anthropic models (older Claude variants) remain available.

For home users who were simply chatting with Claude or using it to help with basic scripting, the change will mostly show up as “this specific version is unavailable” rather than a broader AI blackout.

Removing a high‑end vulnerability‑finding model from broad circulation increases the effort required for less‑resourced cybercriminals to automate discovery of complex bugs in consumer‑facing software and services only by so much. There are other models available on the black market that might be just as effective. And for most cybercriminals, turning a vulnerability into a method they can utilize in an exploit is much more relevant.

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

This month’s Patch Tuesday fixes 206 security flaws in Microsoft software, making it the biggest Patch Tuesday release ever.

The update includes 32 critical vulnerabilities, as well as three publicly disclosed zero-days. Microsoft classifies these as zero-days because information about the vulnerabilities became public before patches were available. None are known to have been actively exploited by attackers.

The huge number of fixed vulnerabilities makes this the largest Patch Tuesday since Microsoft launched the program in October 2003. The company introduced the monthly update schedule after the Blaster worm caused disruption in the early days of Windows.

How to apply patches and check if you’re protected

These updates fix security problems and keep your Windows PC protected. Here’s how to make sure you’re up to date:

1. Open Settings

• Click the Start button (the Windows logo at the bottom left of your screen).
• Click on Settings (it looks like a little gear).

2. Go to Windows Update

• In the Settings window, select Windows Update (usually at the bottom of the menu on the left).

3. Check for updates

• Click the button that says Check for updates.
• Windows will search for the latest Patch Tuesday updates.
• If you have selected to get the latest updates as soon as they’re available, you may see this under More options.
  In which case you may see a Restart required message. Restart your system and the update will complete.
  
• If not, continue with the steps below.

4. Download and install

• If updates are found, they’ll start downloading automatically. Once complete, you’ll see a button that says Install or Restart now.
• Click Install if needed and follow any prompts. Your computer will usually need a restart to finish the update. If it does, click Restart now.

5. Double-check you’re up to date

• After restarting, go back to Windows Update and check again. If it says You’re up to date, you’re all set!

Technical details

One publicly disclosed vulnerability is important to mention. This flaw in Windows BitLocker is tracked as CVE-2026-50507 (CVSS score: 6.8 out of 10) and its description states:

“a protection mechanism failure in Windows BitLocker allows an unauthorized attacker to bypass a security feature with a physical attack.”

BitLocker is a built-in Windows security feature that encrypts your entire hard drive, securing your data from unauthorized access if your device is lost or stolen. However, this vulnerability could allow an attacker with physical access to bypass BitLocker Device Encryption and gain access to encrypted data.

Another is CVE-2026-49160 (CVSS score: 7.5 out of 10) in HTTP.sys. This vulnerability can be exploited to launch a remote denial-of-service attack against major web servers using a technique called HTTP/2 Bomb.

The third to discuss is CVE-2026-45586 (CVSS score: 7.8 out of 10) in the Windows Collaborative Translation Framework (CTFMON). An attacker who successfully exploited this vulnerability could gain SYSTEM privileges. These elevation of privilege (EoP) vulnerabilities are especially valuable to attackers because they can be combined with other flaws to gain full control of a compromised system.

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

This month’s Patch Tuesday fixes 206 security flaws in Microsoft software, making it the biggest Patch Tuesday release ever.

The update includes 32 critical vulnerabilities, as well as three publicly disclosed zero-days. Microsoft classifies these as zero-days because information about the vulnerabilities became public before patches were available. None are known to have been actively exploited by attackers.

The huge number of fixed vulnerabilities makes this the largest Patch Tuesday since Microsoft launched the program in October 2003. The company introduced the monthly update schedule after the Blaster worm caused disruption in the early days of Windows.

How to apply patches and check if you’re protected

These updates fix security problems and keep your Windows PC protected. Here’s how to make sure you’re up to date:

1. Open Settings

• Click the Start button (the Windows logo at the bottom left of your screen).
• Click on Settings (it looks like a little gear).

2. Go to Windows Update

• In the Settings window, select Windows Update (usually at the bottom of the menu on the left).

3. Check for updates

• Click the button that says Check for updates.
• Windows will search for the latest Patch Tuesday updates.
• If you have selected to get the latest updates as soon as they’re available, you may see this under More options.
  In which case you may see a Restart required message. Restart your system and the update will complete.
  
• If not, continue with the steps below.

4. Download and install

• If updates are found, they’ll start downloading automatically. Once complete, you’ll see a button that says Install or Restart now.
• Click Install if needed and follow any prompts. Your computer will usually need a restart to finish the update. If it does, click Restart now.

5. Double-check you’re up to date

• After restarting, go back to Windows Update and check again. If it says You’re up to date, you’re all set!

Technical details

One publicly disclosed vulnerability is important to mention. This flaw in Windows BitLocker is tracked as CVE-2026-50507 (CVSS score: 6.8 out of 10) and its description states:

“a protection mechanism failure in Windows BitLocker allows an unauthorized attacker to bypass a security feature with a physical attack.”

BitLocker is a built-in Windows security feature that encrypts your entire hard drive, securing your data from unauthorized access if your device is lost or stolen. However, this vulnerability could allow an attacker with physical access to bypass BitLocker Device Encryption and gain access to encrypted data.

Another is CVE-2026-49160 (CVSS score: 7.5 out of 10) in HTTP.sys. This vulnerability can be exploited to launch a remote denial-of-service attack against major web servers using a technique called HTTP/2 Bomb.

The third to discuss is CVE-2026-45586 (CVSS score: 7.8 out of 10) in the Windows Collaborative Translation Framework (CTFMON). An attacker who successfully exploited this vulnerability could gain SYSTEM privileges. These elevation of privilege (EoP) vulnerabilities are especially valuable to attackers because they can be combined with other flaws to gain full control of a compromised system.

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

Mozilla has published release notes for Firefox browser version 151.0, and this update includes several genuinely meaningful privacy and security improvements.

Three changes stand out in particular:

• Stronger anti‑fingerprinting
• Broader protection for local network access
• More control over private sessions and permissions

Note that Mozilla says several Firefox 151 features are “part of a progressive roll out,” meaning they will appear for some users first and be expanded over time. So, you may not see all of them immediately.

Privacy

One of the more visible additions is a new “end private session” control in Private Browsing Mode. Instead of closing every private window to clear your traces, you now get a dedicated fire‑icon button next to the address bar that wipes the current private session’s data and immediately starts a fresh one.

Under the hood, this clears the usual private browsing artifacts for that session, including history, cookies, cached files, and other site data that would normally disappear only when the last private window closes.

For people who routinely mix normal and private windows, this is safer and less error‑prone than hunting down every private tab before you walk away from the machine.

Firefox 151 also tightens its defenses against browser fingerprinting in the default “Standard” Enhanced Tracking Protection (ETP) mode. Mozilla says Firefox now limits the amount of device and browser information exposed to websites in a way that reduces the number of uniquely identifiable users by about 14% overall, and by roughly 49% on macOS.

This makes it harder for trackers to pick you out of the crowd, especially on platforms with fewer users to begin with (like certain macOS configurations). This reduces the privacy risk surface by default, which makes it harder for phishing and landing pages that redirect visitors to “categorize” you.

Another important change is Firefox’s “local network access restrictions,” which are now rolling out to all users, not just those who turned Enhanced Tracking Protection to Strict.

This means that when a website wants to communicate with devices on your local network, or with apps and services running on your machine, Firefox now asks for permission first. Chrome and Edge have been rolling out similar permission prompts.

Security

Firefox 151 also quietly fixes several security vulnerabilities.

The most notable example is CVE‑2026‑8953, a sandbox escape due to a use‑after‑free in the Disability Access APIs component. While there are currently no reports of in‑the‑wild exploitation for this specific bug at the time of writing, this is the kind of bug cybercriminals love.

A use-after-free (UAF) is a software memory vulnerability where a program attempts to access a memory location after it has been freed. If the program fails to clear the pointer to that freed memory, attackers can manipulate the error to crash the system or execute arbitrary code. A memory corruption leading to a sandbox escape is exactly the kind of link attackers want to complete a browser exploit chain.

How to update

If you’re running Firefox in a home or small‑office environment, we recommend updating to Firefox 151 as soon as possible to get the fingerprinting protections, local network access prompts, and security patches.

To update Firefox:

• Open Firefox
• Click the menu (three stacked lines) in the upper-right corner
• Go to Help > About Firefox
• Firefox will automatically check for updates and begin downloading them
• Restart the browser when prompted to complete the update

Once your Firefox browser has been updated, it will show a green checkmark along with the message: “Firefox is up to date.”

---

Let’s face it, an incognito window can only do so much. 
 
Breaches, dark web trading, credit fraud. Malwarebytes Identity Theft Protection monitors for all of it, alerts you fast, and comes with identity theft insurance. 

Mozilla has published release notes for Firefox browser version 151.0, and this update includes several genuinely meaningful privacy and security improvements.

Three changes stand out in particular:

• Stronger anti‑fingerprinting
• Broader protection for local network access
• More control over private sessions and permissions

Note that Mozilla says several Firefox 151 features are “part of a progressive roll out,” meaning they will appear for some users first and be expanded over time. So, you may not see all of them immediately.

Privacy

One of the more visible additions is a new “end private session” control in Private Browsing Mode. Instead of closing every private window to clear your traces, you now get a dedicated fire‑icon button next to the address bar that wipes the current private session’s data and immediately starts a fresh one.

Under the hood, this clears the usual private browsing artifacts for that session, including history, cookies, cached files, and other site data that would normally disappear only when the last private window closes.

For people who routinely mix normal and private windows, this is safer and less error‑prone than hunting down every private tab before you walk away from the machine.

Firefox 151 also tightens its defenses against browser fingerprinting in the default “Standard” Enhanced Tracking Protection (ETP) mode. Mozilla says Firefox now limits the amount of device and browser information exposed to websites in a way that reduces the number of uniquely identifiable users by about 14% overall, and by roughly 49% on macOS.

This makes it harder for trackers to pick you out of the crowd, especially on platforms with fewer users to begin with (like certain macOS configurations). This reduces the privacy risk surface by default, which makes it harder for phishing and landing pages that redirect visitors to “categorize” you.

Another important change is Firefox’s “local network access restrictions,” which are now rolling out to all users, not just those who turned Enhanced Tracking Protection to Strict.

This means that when a website wants to communicate with devices on your local network, or with apps and services running on your machine, Firefox now asks for permission first. Chrome and Edge have been rolling out similar permission prompts.

Security

Firefox 151 also quietly fixes several security vulnerabilities.

The most notable example is CVE‑2026‑8953, a sandbox escape due to a use‑after‑free in the Disability Access APIs component. While there are currently no reports of in‑the‑wild exploitation for this specific bug at the time of writing, this is the kind of bug cybercriminals love.

A use-after-free (UAF) is a software memory vulnerability where a program attempts to access a memory location after it has been freed. If the program fails to clear the pointer to that freed memory, attackers can manipulate the error to crash the system or execute arbitrary code. A memory corruption leading to a sandbox escape is exactly the kind of link attackers want to complete a browser exploit chain.

How to update

If you’re running Firefox in a home or small‑office environment, we recommend updating to Firefox 151 as soon as possible to get the fingerprinting protections, local network access prompts, and security patches.

To update Firefox:

• Open Firefox
• Click the menu (three stacked lines) in the upper-right corner
• Go to Help > About Firefox
• Firefox will automatically check for updates and begin downloading them
• Restart the browser when prompted to complete the update

Once your Firefox browser has been updated, it will show a green checkmark along with the message: “Firefox is up to date.”

---

Let’s face it, an incognito window can only do so much. 
 
Breaches, dark web trading, credit fraud. Malwarebytes Identity Theft Protection monitors for all of it, alerts you fast, and comes with identity theft insurance. 

This month’s Patch Tuesday remedies 137 security vulnerabilities, including 31 marked critical by Microsoft, with no zero-days actively exploited in the wild.

Microsoft defines a zero-day as “a flaw in software for which no official patch or security update is available yet.” This month, Microsoft has not observed any included vulnerability being exploited in production environments.

Still, this release is far from low-risk. A large chunk of the critical bugs allow remote code execution (RCE) across Windows services, Office, Azure, SharePoint, and graphics components. That means attackers who trick a user into opening a malicious document or lure them into connecting to a malicious service could gain full control of a system.

Two vulnerabilities to prioritize

From that list, we selected two that look like they could cause some trouble.

First is CVE-2026-40361, which has a CVSS score of 8.4 out of 10. It’s described as a critical use-after-free vulnerability in Microsoft Word that could allow an attacker to execute code locally on the affected system.

Use-after-free is a class of vulnerability caused by incorrect use of dynamic memory during a program’s operation. If, after freeing a memory location, a program does not clear the pointer to that memory, an attacker may be able to use the error to manipulate the program.

So, if an attacker convinces a user to open a malicious Word document, or even previews the file, they could execute arbitrary code with the privileges of the current user. That’s often enough to install malware, steal credentials, or move laterally through a network.

Second is CVE-2026-35421 (CVSS score 7.8 out of 10). This is a critical heap-based buffer overflow in Windows Graphics Device Interface (GDI). A buffer overflow occurs when an area of memory within a software application reaches its address boundary and writes into an adjacent memory region. Microsoft notes:

“For this vulnerability to be exploited, a user would need to open or otherwise process a specially crafted Enhanced Metafile (EMF) file using Microsoft Paint. This action is necessary to trigger the affected graphics functionality in the Windows component.”

---

---

How to apply fixes and check if you’re protected

These updates fix security problems and keep your Windows PC protected. Here’s how to make sure you’re up to date:

1. Open Settings

• Click the Start button (the Windows logo at the bottom left of your screen).
• Click on Settings (it looks like a little gear).

2. Go to Windows Update

• In the Settings window, select Windows Update (usually at the bottom of the menu on the left).

3. Check for updates

• Click the button that says Check for updates.
• Windows will search for the latest Patch Tuesday updates.
• If you have selected to get the latest updates as soon as they’re available, you may see this under More options.
• In which case you may see a Restart required message. Restart your system and the update will complete.
  
• If not, continue with the steps below.

4. Download and Install If updates are found, they’ll start downloading automatically. Once complete, you’ll see a button that says Install or Restart now.

• Click Install if needed and follow any prompts. Your computer will usually need a restart to finish the update. If it does, click Restart now.

5. Double-check you’re up to date

• After restarting, go back to Windows Update and check again. If it says You’re up to date, you’re all set!

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

This month’s Patch Tuesday remedies 137 security vulnerabilities, including 31 marked critical by Microsoft, with no zero-days actively exploited in the wild.

Microsoft defines a zero-day as “a flaw in software for which no official patch or security update is available yet.” This month, Microsoft has not observed any included vulnerability being exploited in production environments.

Still, this release is far from low-risk. A large chunk of the critical bugs allow remote code execution (RCE) across Windows services, Office, Azure, SharePoint, and graphics components. That means attackers who trick a user into opening a malicious document or lure them into connecting to a malicious service could gain full control of a system.

Two vulnerabilities to prioritize

From that list, we selected two that look like they could cause some trouble.

First is CVE-2026-40361, which has a CVSS score of 8.4 out of 10. It’s described as a critical use-after-free vulnerability in Microsoft Word that could allow an attacker to execute code locally on the affected system.

Use-after-free is a class of vulnerability caused by incorrect use of dynamic memory during a program’s operation. If, after freeing a memory location, a program does not clear the pointer to that memory, an attacker may be able to use the error to manipulate the program.

So, if an attacker convinces a user to open a malicious Word document, or even previews the file, they could execute arbitrary code with the privileges of the current user. That’s often enough to install malware, steal credentials, or move laterally through a network.

Second is CVE-2026-35421 (CVSS score 7.8 out of 10). This is a critical heap-based buffer overflow in Windows Graphics Device Interface (GDI). A buffer overflow occurs when an area of memory within a software application reaches its address boundary and writes into an adjacent memory region. Microsoft notes:

“For this vulnerability to be exploited, a user would need to open or otherwise process a specially crafted Enhanced Metafile (EMF) file using Microsoft Paint. This action is necessary to trigger the affected graphics functionality in the Windows component.”

---

---

How to apply fixes and check if you’re protected

These updates fix security problems and keep your Windows PC protected. Here’s how to make sure you’re up to date:

1. Open Settings

• Click the Start button (the Windows logo at the bottom left of your screen).
• Click on Settings (it looks like a little gear).

2. Go to Windows Update

• In the Settings window, select Windows Update (usually at the bottom of the menu on the left).

3. Check for updates

• Click the button that says Check for updates.
• Windows will search for the latest Patch Tuesday updates.
• If you have selected to get the latest updates as soon as they’re available, you may see this under More options.
• In which case you may see a Restart required message. Restart your system and the update will complete.
  
• If not, continue with the steps below.

4. Download and Install If updates are found, they’ll start downloading automatically. Once complete, you’ll see a button that says Install or Restart now.

• Click Install if needed and follow any prompts. Your computer will usually need a restart to finish the update. If it does, click Restart now.

5. Double-check you’re up to date

• After restarting, go back to Windows Update and check again. If it says You’re up to date, you’re all set!

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

Meta has published a new security advisory for messaging app WhatsApp, announcing patches for two vulnerabilities.

WhatsApp has fixed two security flaws that could be abused to interfere with how media and attachments are handled on your device. There is no evidence that either bug has been exploited in the wild.

These bugs don’t automatically infect devices, but they lower the barrier for social engineering and could be chained with other vulnerabilities for more serious attacks.

Malicious messages

The first issue, tracked as CVE‑2026‑23866, affects how WhatsApp processes AI‑generated “rich response messages” that embed Instagram Reels. On affected iOS and Android versions, incomplete validation means a specially crafted message could cause the app to load media from an attacker‑controlled URL. In some cases, this could trigger operating system‑level custom URL scheme handlers.

In other words: a booby‑trapped message could prompt your device to open content from an untrusted source.

How to update WhatsApp for Android

You can easily update WhatsApp from the Google Play Store.

1. Open the Google Play Store
2. Search for WhatsApp Messenger
3. Tap Update

Note: Updates may not be available immediately in all regions.

How to update WhatsApp on iOS

To update WhatsApp on iOS:

• Open the App Store
• Tap your profile icon
• Scroll to find WhatsApp and tap Update

If it’s not listed, search for WhatsApp to check if an “Update” button is available.

Misleading filenames

The second bug, CVE‑2026‑23863, affects WhatsApp for Windows before version 2.3000.1032164386.258709.

In this case, WhatsApp did not correctly handle filenames containing embedded NUL bytes. This could allow a file to appear as a harmless type in the interface while actually being treated as an executable when opened. That’s a classic recipe for social engineering: “click the PDF,” but get an .exe file.

How to update WhatsApp for Windows

You can find your WhatsApp for Windows version number by clicking on your profile picture and selecting Help and feedback.

If your version number is earlier than 2.3000.1032164386.258709, update via the Microsoft Store:

1. Click the Start menu and search for Microsoft Store to open it
2. Click Library located at the bottom-left corner
3. Find WhatsApp Desktop
4. Click Get Updates or Update

Once installed, restart the app to apply the changes.

Automatic updates on Windows

My WhatsApp was already up to date because I have automatic updates turned on. Here’s how to turn it on:

1. Click the Start menu and search for Microsoft Store to open it
2. Select Profile (your account picture) > Settings
3. Make sure App updates is toggled to On

---

Scammers don’t need to hack you. They just need you to click once. 

Malwarebytes Identity Theft Protection catches suspicious activity before it becomes a problem.

Meta has published a new security advisory for messaging app WhatsApp, announcing patches for two vulnerabilities.

WhatsApp has fixed two security flaws that could be abused to interfere with how media and attachments are handled on your device. There is no evidence that either bug has been exploited in the wild.

These bugs don’t automatically infect devices, but they lower the barrier for social engineering and could be chained with other vulnerabilities for more serious attacks.

Malicious messages

The first issue, tracked as CVE‑2026‑23866, affects how WhatsApp processes AI‑generated “rich response messages” that embed Instagram Reels. On affected iOS and Android versions, incomplete validation means a specially crafted message could cause the app to load media from an attacker‑controlled URL. In some cases, this could trigger operating system‑level custom URL scheme handlers.

In other words: a booby‑trapped message could prompt your device to open content from an untrusted source.

How to update WhatsApp for Android

You can easily update WhatsApp from the Google Play Store.

1. Open the Google Play Store
2. Search for WhatsApp Messenger
3. Tap Update

Note: Updates may not be available immediately in all regions.

How to update WhatsApp on iOS

To update WhatsApp on iOS:

• Open the App Store
• Tap your profile icon
• Scroll to find WhatsApp and tap Update

If it’s not listed, search for WhatsApp to check if an “Update” button is available.

Misleading filenames

The second bug, CVE‑2026‑23863, affects WhatsApp for Windows before version 2.3000.1032164386.258709.

In this case, WhatsApp did not correctly handle filenames containing embedded NUL bytes. This could allow a file to appear as a harmless type in the interface while actually being treated as an executable when opened. That’s a classic recipe for social engineering: “click the PDF,” but get an .exe file.

How to update WhatsApp for Windows

You can find your WhatsApp for Windows version number by clicking on your profile picture and selecting Help and feedback.

If your version number is earlier than 2.3000.1032164386.258709, update via the Microsoft Store:

1. Click the Start menu and search for Microsoft Store to open it
2. Click Library located at the bottom-left corner
3. Find WhatsApp Desktop
4. Click Get Updates or Update

Once installed, restart the app to apply the changes.

Automatic updates on Windows

My WhatsApp was already up to date because I have automatic updates turned on. Here’s how to turn it on:

1. Click the Start menu and search for Microsoft Store to open it
2. Select Profile (your account picture) > Settings
3. Make sure App updates is toggled to On

---

Scammers don’t need to hack you. They just need you to click once. 

Malwarebytes Identity Theft Protection catches suspicious activity before it becomes a problem.

Security researchers are warning about a newly discovered vulnerability in the widely used web server management software cPanel and WebHost Manager (WHM). 

This is a critical, actively exploited authentication-bypass bug in cPanel/WHM that lets attackers gain administrative access to the interface without credentials, potentially take over servers and all hosted sites.

The vulnerability, tracked as CVE-2026-41940, has been added to the Known Exploited Vulnerabilities catalog by the Cybersecurity and Infrastructure Security Agency (CISA), meaning there is evidence it is being used in real-world attacks.

Because cPanel/WHM is used by over a million sites worldwide, including banks and health organizations, the potential impact is huge. In simple terms, the bug can act like a front‑door key to a big chunk of the web’s hosting infrastructure.

cPanel released patches on April 28, 2026, and urged all customers and hosts to update. It said all supported versions after 11.40 are affected, including DNSOnly and WP Squared.

Hosting providers including Namecheap, HostGator, and KnownHost temporarily blocked access to cPanel interfaces while patching, treating this as a critical authentication bypass and reporting exploit attempts going back to late February 2026.

How to stay safe

While it’s up to the hosting companies and website owners to patch as quickly as possible, there are ways to reduce your risk if a site you use is compromised.

As always, limit the data you share with websites to what’s absolutely necessary. Data they don’t have can’t be stolen.

When ordering from an online retailer, don’t tick the box to save your card details for future purchases as they will be stored on the server.

If there’s an option to check out as a guest, use it. It reduces the amount of personal data tied to an account.

Don’t reuse passwords. When one site is compromised, having the same credentials in several places turns it into a multi‑account takeover problem. A password manager can help you create complex unique passphrases, and remember them for you.

Where possible, pay by credit card. In many regions, this gives you stronger fraud protection.

---

---

When a site you trust gets hacked

If you think you’ve been affected by a data breach, take the following steps:

• Check the company’s advice. Every breach is different, so check with the company to find out what’s happened and follow any specific advice it offers.
• Change your password. You can make a stolen password useless to thieves by changing it. Choose a strong password that you don’t use for anything else. Better yet, let a password manager choose one for you.
• Enable two-factor authentication (2FA). If you can, use a FIDO2-compliant hardware key, laptop, or phone as your second factor. Some forms of 2FA can be phished just as easily as a password, but 2FA that relies on a FIDO2 device can’t be phished.
• Watch out for impersonators. The thieves may contact you posing as the breached platform. Check the official website to see if it’s contacting victims and verify the identity of anyone who contacts you using a different communication channel.
• Take your time. Phishing attacks often impersonate people or brands you know, and use themes that require urgent attention, such as missed deliveries, account suspensions, and security alerts.
• Consider not storing your card details. It’s definitely more convenient to let sites remember your card details, but it increases risk if a retailer suffers a breach.
• Set up identity monitoring, which alerts you if your personal information is found being traded illegally online and helps you recover after.

---

Security researchers are warning about a newly discovered vulnerability in the widely used web server management software cPanel and WebHost Manager (WHM). 

This is a critical, actively exploited authentication-bypass bug in cPanel/WHM that lets attackers gain administrative access to the interface without credentials, potentially take over servers and all hosted sites.

The vulnerability, tracked as CVE-2026-41940, has been added to the Known Exploited Vulnerabilities catalog by the Cybersecurity and Infrastructure Security Agency (CISA), meaning there is evidence it is being used in real-world attacks.

Because cPanel/WHM is used by over a million sites worldwide, including banks and health organizations, the potential impact is huge. In simple terms, the bug can act like a front‑door key to a big chunk of the web’s hosting infrastructure.

cPanel released patches on April 28, 2026, and urged all customers and hosts to update. It said all supported versions after 11.40 are affected, including DNSOnly and WP Squared.

Hosting providers including Namecheap, HostGator, and KnownHost temporarily blocked access to cPanel interfaces while patching, treating this as a critical authentication bypass and reporting exploit attempts going back to late February 2026.

How to stay safe

While it’s up to the hosting companies and website owners to patch as quickly as possible, there are ways to reduce your risk if a site you use is compromised.

As always, limit the data you share with websites to what’s absolutely necessary. Data they don’t have can’t be stolen.

When ordering from an online retailer, don’t tick the box to save your card details for future purchases as they will be stored on the server.

If there’s an option to check out as a guest, use it. It reduces the amount of personal data tied to an account.

Don’t reuse passwords. When one site is compromised, having the same credentials in several places turns it into a multi‑account takeover problem. A password manager can help you create complex unique passphrases, and remember them for you.

Where possible, pay by credit card. In many regions, this gives you stronger fraud protection.

---

---

When a site you trust gets hacked

If you think you’ve been affected by a data breach, take the following steps:

• Check the company’s advice. Every breach is different, so check with the company to find out what’s happened and follow any specific advice it offers.
• Change your password. You can make a stolen password useless to thieves by changing it. Choose a strong password that you don’t use for anything else. Better yet, let a password manager choose one for you.
• Enable two-factor authentication (2FA). If you can, use a FIDO2-compliant hardware key, laptop, or phone as your second factor. Some forms of 2FA can be phished just as easily as a password, but 2FA that relies on a FIDO2 device can’t be phished.
• Watch out for impersonators. The thieves may contact you posing as the breached platform. Check the official website to see if it’s contacting victims and verify the identity of anyone who contacts you using a different communication channel.
• Take your time. Phishing attacks often impersonate people or brands you know, and use themes that require urgent attention, such as missed deliveries, account suspensions, and security alerts.
• Consider not storing your card details. It’s definitely more convenient to let sites remember your card details, but it increases risk if a retailer suffers a breach.
• Set up identity monitoring, which alerts you if your personal information is found being traded illegally online and helps you recover after.

---

A researcher has discovered a weakness called PhantomRPC that Microsoft does not consider a vulnerability it plans to patch.

PhantomRPC involves Windows Remote Procedure Call (RPC), the core of communication between Windows processes. The vulnerability lets a process with impersonation rights escalate to SYSTEM by impersonating high‑privileged clients that connect to a fake RPC server.

The researcher presented a detailed technical report outlining five exploitation paths, including coercion, user interaction, or background services. They warned that potential vectors are “effectively unlimited” because the root issue is architectural.

Microsoft, however, classified the issue as “moderate,” refused a bounty, declined to assign a CVE (a spot in the list of Common Vulnerabilities and Exposures), and closed the case without tracking. Its position is that the technique requires an already‑compromised machine and does not provide unauthenticated or remote access.

Experts disagreed with Microsoft’s assessment. Their concern is that Microsoft is downplaying a systemic local privilege escalation technique that exists in all supported Windows versions.

The issue

At the core of this issue is that the Windows RPC runtime does not sufficiently verify that the server a high‑privileged client connects to is the intended legitimate endpoint.

If a legitimate RPC server is not reachable (for example because the service stopped, was misconfigured, not installed, or due to a race condition), an attacker with SeImpersonatePrivilege can spin up a fake RPC server that “fills the gap” using the same interface and endpoint.

When a SYSTEM or high‑privileged client connects to this fake server, using an impersonation level that allows the server to impersonate the client, the attacker can call RpcImpersonateClient and immediately escalate their privileges to SYSTEM.

From Microsoft’s perspective, the ability to run a rogue RPC server in this way falls under the category of “already compromised.”

SeImpersonatePrivilege

To understand the issue better, we need to dig into what SeImpersonatePrivilege does.

Basically, SeImpersonatePrivilege is the Windows permission that lets a program “pretend to be you” after you’ve already logged in, so it can do things on your behalf using your level of access.

It’s needed because many system services and server‑type apps (file sharing, RPC servers, COM servers, web apps) have to perform actions on behalf of a user, like reading their files or applying group policy.

If an attacker gains this privilege, they can create a fake service or server and wait for a more powerful account to talk to it. When that high‑privilege service connects, the attacker can grab its security token and impersonate it, effectively upgrading from an account with lower privileges to full SYSTEM control on that machine.

Protection

A Microsoft spokesperson provided the following statement:

“This technique requires an already-compromised machine and does not grant unauthenticated or remote access. Any update is a balance between existing compatibility and customer risk, and we remain committed to continually hardening our products. We recommend customers follow security best practices, including limiting administrative privileges and applying the principle of least privilege.”

In our opinion, mitigating PhantomRPC properly would require deep changes to the RPC architecture, which is hard to do on existing Windows versions without breaking compatibility. It’s maybe something we’ll see in future versions, given the scale of change needed.

What you can do:

• As PhantomRPC is a piece in a larger chain, it is still very important to keep Windows updated.
• Use your admin account sparingly and only for the tasks that need that kind of privilege.
• Use an up-to-date, real-time anti-malware solution that can detect and block suspicious privilege‑escalation activity.
• Avoid disabling or “hardening” services blindly since a malicious service might step in their place.

To answer the question in the title: it looks like a “feature” that can be abused in many ways; one that has outlived its original threat model. Defenders have to treat them as ongoing risks, rather than one‑off CVEs.

---

---

A researcher has discovered a weakness called PhantomRPC that Microsoft does not consider a vulnerability it plans to patch.

PhantomRPC involves Windows Remote Procedure Call (RPC), the core of communication between Windows processes. The vulnerability lets a process with impersonation rights escalate to SYSTEM by impersonating high‑privileged clients that connect to a fake RPC server.

The researcher presented a detailed technical report outlining five exploitation paths, including coercion, user interaction, or background services. They warned that potential vectors are “effectively unlimited” because the root issue is architectural.

Microsoft, however, classified the issue as “moderate,” refused a bounty, declined to assign a CVE (a spot in the list of Common Vulnerabilities and Exposures), and closed the case without tracking. Its position is that the technique requires an already‑compromised machine and does not provide unauthenticated or remote access.

Experts disagreed with Microsoft’s assessment. Their concern is that Microsoft is downplaying a systemic local privilege escalation technique that exists in all supported Windows versions.

The issue

At the core of this issue is that the Windows RPC runtime does not sufficiently verify that the server a high‑privileged client connects to is the intended legitimate endpoint.

If a legitimate RPC server is not reachable (for example because the service stopped, was misconfigured, not installed, or due to a race condition), an attacker with SeImpersonatePrivilege can spin up a fake RPC server that “fills the gap” using the same interface and endpoint.

When a SYSTEM or high‑privileged client connects to this fake server, using an impersonation level that allows the server to impersonate the client, the attacker can call RpcImpersonateClient and immediately escalate their privileges to SYSTEM.

From Microsoft’s perspective, the ability to run a rogue RPC server in this way falls under the category of “already compromised.”

SeImpersonatePrivilege

To understand the issue better, we need to dig into what SeImpersonatePrivilege does.

Basically, SeImpersonatePrivilege is the Windows permission that lets a program “pretend to be you” after you’ve already logged in, so it can do things on your behalf using your level of access.

It’s needed because many system services and server‑type apps (file sharing, RPC servers, COM servers, web apps) have to perform actions on behalf of a user, like reading their files or applying group policy.

If an attacker gains this privilege, they can create a fake service or server and wait for a more powerful account to talk to it. When that high‑privilege service connects, the attacker can grab its security token and impersonate it, effectively upgrading from an account with lower privileges to full SYSTEM control on that machine.

Protection

A Microsoft spokesperson provided the following statement:

“This technique requires an already-compromised machine and does not grant unauthenticated or remote access. Any update is a balance between existing compatibility and customer risk, and we remain committed to continually hardening our products. We recommend customers follow security best practices, including limiting administrative privileges and applying the principle of least privilege.”

In our opinion, mitigating PhantomRPC properly would require deep changes to the RPC architecture, which is hard to do on existing Windows versions without breaking compatibility. It’s maybe something we’ll see in future versions, given the scale of change needed.

What you can do:

• As PhantomRPC is a piece in a larger chain, it is still very important to keep Windows updated.
• Use your admin account sparingly and only for the tasks that need that kind of privilege.
• Use an up-to-date, real-time anti-malware solution that can detect and block suspicious privilege‑escalation activity.
• Avoid disabling or “hardening” services blindly since a malicious service might step in their place.

To answer the question in the title: it looks like a “feature” that can be abused in many ways; one that has outlived its original threat model. Defenders have to treat them as ongoing risks, rather than one‑off CVEs.

---

---

Apple has released a software update that deals with an issue that could allow deleted notifications to be retrieved. Something that, in at least one reported case, was used by law enforcement during forensic analysis.

Apple fixed the issue in iOS and iPadOS versions 18.7.8 and 26.4.2 (check availability for your device at those links). The update deals with a singular security vulnerability, tracked as CVE-2026-28950.

Although the description is brief—“a logging issue was addressed with improved data redaction”—the impact points us in the right direction.

“Notifications marked for deletion could be unexpectedly retained on the device.”

This suggests that Apple’s bug was that iOS kept copies of notification content in an internal database for longer than intended, even after the messages “disappeared” or the app was uninstalled. In a case reported by 404 Media, law enforcement was able to recover those notifications using standard forensic tools once they had access to the unlocked device. The example in that reported case involved Signal.

---

---

A response on X by Signal states:

“The FBI was able to forensically extract copies of incoming Signal messages from a defendant’s iPhone, even after the app was deleted, because copies of the content were saved in the device’s push notification database.”

Before we go into the update process, you may want to know that you can mute or hide notifications in Signal, which also protects them from prying eyes. In Signal, open your Settings and tap on Notifications. You can adjust several settings there. For example, I have mine set so I only see the name of the sender.

Install the update

For iOS and iPadOS users, you can check if you’re using the latest software version by going to Settings > General > Software Update. It’s also worth turning on Automatic Updates if you haven’t already. You can do that on the same screen.

---

Scammers know more about you than you think. 

Malwarebytes Mobile Security protects you from phishing, scam texts, malicious sites, and more. With real-time AI-powered Scam Guard built right in. 

Download for iOS → Download for Android → 

Apple has released a software update that deals with an issue that could allow deleted notifications to be retrieved. Something that, in at least one reported case, was used by law enforcement during forensic analysis.

Apple fixed the issue in iOS and iPadOS versions 18.7.8 and 26.4.2 (check availability for your device at those links). The update deals with a singular security vulnerability, tracked as CVE-2026-28950.

Although the description is brief—“a logging issue was addressed with improved data redaction”—the impact points us in the right direction.

“Notifications marked for deletion could be unexpectedly retained on the device.”

This suggests that Apple’s bug was that iOS kept copies of notification content in an internal database for longer than intended, even after the messages “disappeared” or the app was uninstalled. In a case reported by 404 Media, law enforcement was able to recover those notifications using standard forensic tools once they had access to the unlocked device. The example in that reported case involved Signal.

---

---

A response on X by Signal states:

“The FBI was able to forensically extract copies of incoming Signal messages from a defendant’s iPhone, even after the app was deleted, because copies of the content were saved in the device’s push notification database.”

Before we go into the update process, you may want to know that you can mute or hide notifications in Signal, which also protects them from prying eyes. In Signal, open your Settings and tap on Notifications. You can adjust several settings there. For example, I have mine set so I only see the name of the sender.

Install the update

For iOS and iPadOS users, you can check if you’re using the latest software version by going to Settings > General > Software Update. It’s also worth turning on Automatic Updates if you haven’t already. You can do that on the same screen.

---

Scammers know more about you than you think. 

Malwarebytes Mobile Security protects you from phishing, scam texts, malicious sites, and more. With real-time AI-powered Scam Guard built right in. 

Download for iOS → Download for Android → 

Apple has released a Background Security Improvement to patch a flaw that could allow malicious websites to bypass browser protections and access data from other sites.

What is it?

The patched WebKit vulnerability is described as:

“A cross-origin issue in the Navigation API was addressed with improved input validation.”

WebKit vulnerabilities refer to security flaws in Apple’s web rendering engine, which powers Safari, Mail, and the App Store on iOS and macOS.

What this means is that the CVE-2026-20643 vulnerability makes it possible for a malicious website to pretend to be another site, maybe one you trust, and then read or steal information that should be kept separate. Normally, browsers enforce a rule called the “same‑origin policy,” which is like a strict fence that stops one site from peeking into another site’s data. This bug could help cybercriminals cut through that fence.

In practical terms, an attacker would first have to lure you to a specially crafted web page. If you visited it, that page could try to bypass the normal isolation between sites and access things it should not see, such as data from another tab or embedded content from a different service.

Attackers do not currently appear to exploit this flaw in the wild, but they like to chain issues like this with other bugs to steal accounts or sensitive data, which likely prompted Apple to ship it as a Background Security Improvement. Apple’s fix tightens how WebKit checks and handles cross‑site navigation.

What to do

This patch for a WebKit vulnerability, tracked as CVE-2026-20643, installs on top of versions 26.3.1/26.3.2 and not as a separate full OS version. Background Security Improvements are only available on the latest OS branch (26.x) and apply silently in the background if you’re on the latest version.

For iOS and iPadOS users, you can check if you’re using the latest software version by  going to Settings > General > Software Update. It’s also worth turning on Automatic Updates if you haven’t already. You can do that on the same screen.

For macOS Tahoe users, you can find out if you’re on the latest 26.3 version from the Apple menu. In the upper-left corner of your screen, choose About This Mac. The information shown there includes the macOS name and version number. If you need to know the build number as well, click the version number to see it.

This Background Security Improvement is only available for Mac users running Tahoe 26.3.1 and MacBook Neo users running 26.3.2.

All users have to do is to check if they have the Background Security Improvements option set to enabled.

For iPhone and iPad users, this setting can be found under Privacy & Security, where you can scroll down and look for the Background Security Improvements toggle.

On a Mac (macOS Tahoe 26.3.+ only), you can check by following these instructions:

1. Click the Apple menu > System Settings.
2. In the sidebar, click Privacy & Security.
3. Scroll down on the right and click Background Security Improvements.
4. Make sure Automatically Install is turned on. If it’s off, the Mac won’t get Background Security Improvements until the fixes are rolled into a later full update.

The Install option in my screenshot means that you can speed up the process by clicking it. But it’s fine to wait until it happens automatically.

After the update, your OS version should show 26.3.1 (a), except for MacBook Neos which should be at 26.3.2 (a).

---

We don’t just report on phone security—we provide it

Cybersecurity risks should never spread beyond a headline. Keep threats off your mobile devices by downloading Malwarebytes for iOS, and Malwarebytes for Android today.

A researcher published “Zombie ZIP,” a simple way to change the first part (header) of a ZIP file so it falsely claims its contents are uncompressed while they are actually compressed.

Many antivirus products trust that header and never properly decompress or inspect the real payload. In tests conducted about a week after disclosure, around 60 of 63 common antivirus suites failed to detect malware hidden this way—roughly 95% of engines let it pass.

Zombie ZIP is essentially a method to create a malformed ZIP file that can bypass detection by most antivirus scanners. The technique has a major caveat, though. The malformed ZIP file requires a custom loader to open it correctly. Any normal archive utility like the built-in Windows extractor, 7-zip, WinRAR, and others will also flag the file as malformed.

The vulnerability is tracked as CVE-2026-0866, although several cybersecurity researchers dispute whether it should be categorized as a vulnerability or assigned a CVE at all. The fact that it requires a custom loader makes it almost impossible for this method to infect a system that is not already compromised.

It still allows anti-malware solutions to detect both the custom loader and any known malware once the payload is properly decompressed. In other words, the bypass only affects the initial inspection of the ZIP file, not the actual execution of already known malware.

Malwarebytes/ThreatDown products detected both files, by the way.

Technical details

On their GitHub page (currently blocked by Malwarebytes Browser Guard due to a risky pattern), the researchers explain how the Zombie ZIP method works.

By changing the file’s compressiontype to 0 (STORED), tools trying to read the archive assume the file’s contents are simply stored inside the ZIP file and not compressed.

“AV engines trust the ZIP Method field. When Method=0 (STORED), they scan the data as raw uncompressed bytes. But the data is actually DEFLATE compressed — so the scanner sees compressed noise and finds no signatures.

The CRC is set to the uncompressed payload’s checksum, creating an additional mismatch that causes standard extraction tools (7-Zip, unzip, WinRAR) to report errors or extract corrupted output.

However, a purpose-built loader that ignores the declared method and decompresses as DEFLATE recovers the payload perfectly.

The vulnerability is scanner evasion: security controls assert ‘no malware present’ while malware is present and trivially recoverable by attacker tooling.”

Security researcher Didier Stevens published a method to safely examine the content of a malformed Zombie ZIP file. One way to spot the manipulation is by comparing the ZIP header fields compressedsize and uncompressedsize. If they are different, that means the ZIP file is not actually STORED, but compressed.

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

A researcher published “Zombie ZIP,” a simple way to change the first part (header) of a ZIP file so it falsely claims its contents are uncompressed while they are actually compressed.

Many antivirus products trust that header and never properly decompress or inspect the real payload. In tests conducted about a week after disclosure, around 60 of 63 common antivirus suites failed to detect malware hidden this way—roughly 95% of engines let it pass.

Zombie ZIP is essentially a method to create a malformed ZIP file that can bypass detection by most antivirus scanners. The technique has a major caveat, though. The malformed ZIP file requires a custom loader to open it correctly. Any normal archive utility like the built-in Windows extractor, 7-zip, WinRAR, and others will also flag the file as malformed.

The vulnerability is tracked as CVE-2026-0866, although several cybersecurity researchers dispute whether it should be categorized as a vulnerability or assigned a CVE at all. The fact that it requires a custom loader makes it almost impossible for this method to infect a system that is not already compromised.

It still allows anti-malware solutions to detect both the custom loader and any known malware once the payload is properly decompressed. In other words, the bypass only affects the initial inspection of the ZIP file, not the actual execution of already known malware.

Malwarebytes/ThreatDown products detected both files, by the way.

Technical details

On their GitHub page (currently blocked by Malwarebytes Browser Guard due to a risky pattern), the researchers explain how the Zombie ZIP method works.

By changing the file’s compressiontype to 0 (STORED), tools trying to read the archive assume the file’s contents are simply stored inside the ZIP file and not compressed.

“AV engines trust the ZIP Method field. When Method=0 (STORED), they scan the data as raw uncompressed bytes. But the data is actually DEFLATE compressed — so the scanner sees compressed noise and finds no signatures.

The CRC is set to the uncompressed payload’s checksum, creating an additional mismatch that causes standard extraction tools (7-Zip, unzip, WinRAR) to report errors or extract corrupted output.

However, a purpose-built loader that ignores the declared method and decompresses as DEFLATE recovers the payload perfectly.

The vulnerability is scanner evasion: security controls assert ‘no malware present’ while malware is present and trivially recoverable by attacker tooling.”

Security researcher Didier Stevens published a method to safely examine the content of a malformed Zombie ZIP file. One way to spot the manipulation is by comparing the ZIP header fields compressedsize and uncompressedsize. If they are different, that means the ZIP file is not actually STORED, but compressed.

---

We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

Last week on Malwarebytes Labs:

• Watch out for fake Malwarebytes renewal notices in your calendar
• Google patches two Chrome zero-days under active attack. Update now
• Attackers impersonate Temu in ClickFix $Temu airdrop scam
• Apple patches Coruna exploit kit flaws for older iOS versions
• This Android vulnerability can break your lock screen in under 60 seconds
• Microsoft Authenticator could leak login codes—update your app now
• Meta rolls out anti-scam tools across WhatsApp, Facebook, and Messenger
• Phishers hide scam links with IPv6 trick in “free toothbrush” emails
• Sextortion “I recorded you” emails reuse passwords found in disposable inboxes
• Watch out for tax-season robocalls pushing fake “relief programs”
• March 2026 Patch Tuesday fixes two zero-day vulnerabilities
• How to see your Google Search history (and delete it)
• Signal and WhatsApp accounts targeted in phishing campaign
• Hackers may have breached FBI wiretap network via supply chain
• Fake Claude Code install pages hit Windows and Mac users with infostealers
• Quiz sites trick users into enabling unwanted browser notifications

Stay safe!

---

We don’t just report on scams—we help detect them

Cybersecurity risks should never spread beyond a headline. If something looks dodgy to you, check if it’s a scam using Malwarebytes Scam Guard. Submit a screenshot, paste suspicious content, or share a link, text or phone number, and we’ll tell you if it’s a scam or legit. Available with Malwarebytes Premium Security for all your devices, and in the Malwarebytes app for iOS and Android.