Microsoft is investigating a new issue preventing third-party applications from launching Microsoft Office applications or opening documents on up-to-date Windows systems. [...]

Microsoft confirmed that it's working on a security patch for a Defender zero-day vulnerability named "RoguePlanet," disclosed one week ago. [...]

Microsoft has created an open-source fork of Windows Terminal called "Intelligent Terminal," and it allows you to use AI directly inside Terminal without interfering with the regular session. [...]

An anonymous security researcher called “Nightmare Eclipse” has been publishing a series of significant security exploits against Microsoft Windows—including one that breaks BitLocker. Microsoft has threatened legal action against the researcher. Lots of recriminations are being traded back and forth.

The bugs could be exploited to elevate privileges to System or create a denial-of-service (DoS) condition.

The post Microsoft Patches Exploited UnDefend and RedSun Defender Zero-Days appeared first on SecurityWeek.

On Wednesday, Microsoft started rolling out security patches for two Defender vulnerabilities that have been exploited in zero-day attacks. [...]

Microsoft says it dismantled a malware-signing-as-a-service (MSaaS) called Fox Tempest, which helped cybercriminals make malware appear legitimate.

The service let customers submit malicious files to be digitally signed with short-lived Microsoft-issued certificates, making the malware look legitimate and more likely to bypass security checks.

Fox Tempest’s service was built around a customer-facing signing workflow where cybercriminals could upload malicious binaries to a portal, have them signed with certificates valid for only 72 hours, and then receive files that appeared to come from a trusted software source.

Microsoft explicitly says this approach allowed malware to evade security controls and bypass defenses that would otherwise flag suspicious unsigned code. Many security tools treat signed binaries as more trustworthy than unsigned ones, especially in environments that rely on allow-lists and publisher reputation. Fox Tempest abused that assumption by using fraudulently obtained certificates to make malware blend in as legitimate software, increasing the likelihood of execution and successful delivery.

A trusted-looking certificate can help malware get past initial scrutiny, especially when paired with social engineering, paid ads, SEO poisoning, or fake download pages. In this campaign, the signing layer helped malicious installers masquerade as products like AnyDesk, Teams, PuTTY, and Webex, which is exactly the kind of abuse that can slip through control frameworks built around reputation and trust.

The fraudulent certificates were used to spread ransomware and infostealers. The effects of these malware campaigns were broad, with attacks affecting healthcare, education, government, and financial services across multiple countries.

How to stay safe

Microsoft’s disclosure shows how cybercrime has evolved beyond “malware authors” into a service economy where one group specializes in producing trust and others monetize it.

For defenders, the strongest lesson is not to treat code signing as a standalone security control. 

For consumers:

• Remember to only download software from the official vendor site, the Microsoft Store, or another source you already trust. Avoid download buttons on links sent via social media posts, direct messages or email.
• Be skeptical of “sponsored” search results and advertisements for popular apps.
• Use an up-to-date, real-time anti-malware solution that looks for malicious behavior rather than just signatures.

---

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.

Microsoft says it dismantled a malware-signing-as-a-service (MSaaS) called Fox Tempest, which helped cybercriminals make malware appear legitimate.

The service let customers submit malicious files to be digitally signed with short-lived Microsoft-issued certificates, making the malware look legitimate and more likely to bypass security checks.

Fox Tempest’s service was built around a customer-facing signing workflow where cybercriminals could upload malicious binaries to a portal, have them signed with certificates valid for only 72 hours, and then receive files that appeared to come from a trusted software source.

Microsoft explicitly says this approach allowed malware to evade security controls and bypass defenses that would otherwise flag suspicious unsigned code. Many security tools treat signed binaries as more trustworthy than unsigned ones, especially in environments that rely on allow-lists and publisher reputation. Fox Tempest abused that assumption by using fraudulently obtained certificates to make malware blend in as legitimate software, increasing the likelihood of execution and successful delivery.

A trusted-looking certificate can help malware get past initial scrutiny, especially when paired with social engineering, paid ads, SEO poisoning, or fake download pages. In this campaign, the signing layer helped malicious installers masquerade as products like AnyDesk, Teams, PuTTY, and Webex, which is exactly the kind of abuse that can slip through control frameworks built around reputation and trust.

The fraudulent certificates were used to spread ransomware and infostealers. The effects of these malware campaigns were broad, with attacks affecting healthcare, education, government, and financial services across multiple countries.

How to stay safe

Microsoft’s disclosure shows how cybercrime has evolved beyond “malware authors” into a service economy where one group specializes in producing trust and others monetize it.

For defenders, the strongest lesson is not to treat code signing as a standalone security control. 

For consumers:

• Remember to only download software from the official vendor site, the Microsoft Store, or another source you already trust. Avoid download buttons on links sent via social media posts, direct messages or email.
• Be skeptical of “sponsored” search results and advertisements for popular apps.
• Use an up-to-date, real-time anti-malware solution that looks for malicious behavior rather than just signatures.

---

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.

Microsoft has shared mitigations for YellowKey, a recently disclosed Windows BitLocker zero-day vulnerability that grants access to protected drives. [...]

A threat actor targeting Microsoft 365 and Azure production environments is stealing data in attacks that abuse legitimate applications and administration features. [...]

Microsoft plans to raise the quality bar of Windows 11 drivers, as drivers "sit at the heart of every Windows experience" and connect the OS to the "silicon, components, and peripherals." [...]

Microsoft has confirmed user reports that the Teams team collaboration app is displaying non-dismissible location prompts on some macOS systems. [...]

 Fox Tempest provides a service that cybercriminals use to distribute ransomware and other malware disguised as legitimate software.

The post Microsoft Disrupts Malware-Signing Service Run by ‘Fox Tempest’  appeared first on SecurityWeek.

Microsoft says customers in restricted network environments may encounter Windows Update failures after installing the January 2026 optional non-security preview updates. [...]

Microsoft has finally brought back the resizable taskbar and Start menu to Windows 11 in the latest preview version rolling out to Insiders in the Experimental channel. [...]

Microsoft has confirmed that the May 2026 Windows 11 security update (KB5089549) fails to install on some systems and triggers 0x800f0922 errors. [...]

A cybersecurity researcher has released a proof-of-concept exploit for a Windows privilege escalation zero-day dubbed "MiniPlasma" that lets attackers gain SYSTEM privileges on fully patched Windows systems.  [...]

​During the second day of Pwn2Own Berlin 2026, competitors collected $385,750 in cash awards after exploiting 15 unique zero-day vulnerabilities in multiple products, including Windows 11, Microsoft Exchange, and Red Hat Enterprise Linux for Workstations. [...]

Artificial intelligence platforms may be just as susceptible to social engineering as human beings, but they are proving remarkably good at finding security vulnerabilities in human-made computer code. That reality is on full display this month with some of the more widely-used software makers — including Apple, Google, Microsoft, Mozilla and Oracle — fixing near record volumes of security bugs, and/or quickening the tempo of their patch releases.

As it does on the second Tuesday of every month, Microsoft today released software updates to address at least 118 security vulnerabilities in its various Windows operating systems and other products. Remarkably, this is the first Patch Tuesday in nearly two years that Microsoft is not shipping any fixes to deal with emergency zero-day flaws that are already being exploited. Nor have any of the flaws fixed today been previously disclosed (potentially giving attackers a heads up in how to exploit the weakness).

Sixteen of the vulnerabilities earned Microsoft’s most-dire “critical” label, meaning malware or miscreants could abuse these bugs to seize remote control over a vulnerable Windows device with little or no help from the user. Rapid7 has done much of the heavy lifting in identifying some of the more concerning critical weaknesses this month, including:

• CVE-2026-41089: A critical stack-based buffer overflow in Windows Netlogon that offers an attacker SYSTEM privileges on the domain controller. No privileges or user interaction are required, and attack complexity is low. Patches are available for all versions of Windows Server from 2012 onwards.
• CVE-2026-41096: A critical RCE in the Windows DNS client implementation worthy of attention despite Microsoft assessing exploitation as less likely.
• CVE-2026-41103: A critical elevation of privilege vulnerability that allows an unauthorized attacker to impersonate an existing user by presenting forged credentials, thus bypassing Entra ID. Microsoft expects that exploitation is more likely.

May’s Patch Tuesday is a welcome respite from April, which saw Microsoft fix a near-record 167 security flaws. Microsoft was among a few dozen tech giants given access to a “Project Glasswing,” a much-hyped AI capability developed by Anthropic that appears quite effective at unearthing security vulnerabilities in code.

Apple, another early participant in Project Glasswing, typically fixes an average of 20 vulnerabilities each time it ships a security update for iOS devices, said Chris Goettl, vice president of product management at Ivanti. On May 11, Apple shipped updates to address at least 52 vulnerabilities and backported the changes all the way to iPhone 6s and iOS 15.

Last month, Mozilla released Firefox 150, which resolved a whopping 271 vulnerabilities that were reportedly discovered during the Glasswing evaluation.

“Since Firefox 150.0.0 released, they have been on a more aggressive weekly cadence for security updates including the release of Firefox 150.0.3 on May Patch Tuesday resolving between three to five CVEs in each release,” Goettl said.

The software giant Oracle likewise recently increased its patch pace in response to their work with Glasswing. In its most recent quarterly patch update, Oracle addressed at least 450 flaws, including more than 300 fixes for remotely exploitable, unauthenticated flaws. But at the end of April, Oracle announced it was switching to a monthly update cycle for critical security issues.

On May 8, Google started rolling out updates to its Chrome browser that fixed an astonishing 127 security flaws (up from just 30 the previous month). Chrome automagically downloads available security updates, but installing them requires fully restarting the browser.

If you encounter any weirdness applying the updates from Microsoft or any other vendor mentioned here, feel free to sound off in the comments below. Meantime, if you haven’t backed up your data and/or drive lately, doing that before updating is generally sound advice. For a more granular look at the Microsoft updates released today, checkout this inventory by the SANS Internet Storm Center.

Unit 42 analyzes AD CS exploitation through template misconfigurations and shadow credential misuse while offering behavioral detection for defenders.

The post Inside AD CS Escalation: Unpacking Advanced Misuse Techniques and Tools appeared first on Unit 42.