October 2025 Windows 11 Security and Feature Updates Deployment
Microsoft released cumulative updates KB5066835 and KB5066793 for Windows 11 versions 25H2/24H2 and 23H2 as part of the October 2025 Patch Tuesday. These updates are mandatory and address a range of security vulnerabilities discovered in previous months, ensuring that systems remain protected against the latest threats. The updates can be installed automatically through Windows Update or manually via the Microsoft Update Catalog, providing flexibility for both end users and enterprise administrators. After installation, the build numbers for Windows 11 25H2 and 24H2 are updated to Build 26200.6899 and 26100.6899, respectively, while 23H2 is updated to 226x1.6050. This release marks the first Patch Tuesday update for version 25H2, which shares its codebase with 24H2, resulting in identical fixes and improvements across both versions. Notably, this is the penultimate update for Windows 11 23H2, as its support is scheduled to end in November 2025. The update resolves several issues, including a bug that caused the print preview screen to freeze in Chromium-based browsers, and a problem where apps and games became unresponsive if users signed in with only a Gamepad at the lock screen. PowerShell Remoting and Windows Remote Management (WinRM) timeouts have been addressed, improving reliability for remote administration tasks. An issue preventing audit events from being logged has also been fixed, enhancing system monitoring and compliance. The update improves the setup process for Windows Hello face recognition, particularly when using USB infrared camera modules, ensuring smoother biometric authentication. Microsoft emphasizes the importance of keeping security intelligence up to date in its antimalware products, such as Microsoft Defender Antivirus, to maintain robust protection against evolving threats. Security intelligence updates are delivered automatically via Windows Update, but users and administrators can also trigger manual updates to ensure immediate coverage. These updates leverage cloud-based protection and AI-enhanced detection to rapidly identify and mitigate new malware and attack techniques. Microsoft provides troubleshooting resources for users experiencing issues with automatic updates, ensuring that security patches and intelligence updates are applied promptly. The integration of third-party materials in security intelligence updates is disclosed, maintaining transparency in the update process. Overall, the October 2025 Patch Tuesday updates represent a comprehensive effort by Microsoft to address security vulnerabilities, improve system stability, and enhance user experience across supported Windows 11 versions.
Get ahead of threats like this
Mallory correlates global threat intelligence with your attack surface — know if you’re exposed before adversaries strike.
How this story unfolded
2 events from the most recent confirmed update back to the earliest known activity.
Microsoft publishes updated Defender Antivirus security intelligence
Microsoft published updated security intelligence definitions for Microsoft Defender Antivirus and other Microsoft antimalware products. The reference indicates a definitions update but does not specify the exact signatures or threats covered.
Microsoft releases Windows 11 KB5066835 and KB5066793 updates
Microsoft released the Windows 11 cumulative updates KB5066835 and KB5066793. The reference does not provide additional technical details about fixes or impact beyond the release itself.
Sources
2 references tracked. Mallory keeps watching after this page renders.
See the full picture, correlated to your attack surface.
Map indicators from this story to your assets and identify affected systems in minutes.
Every observed campaign, victim, and pivot linked to actors named in this story.
Malware, exploits, and IOCs connected to the activity described here.
YARA, Sigma, and Snort rules deployed to your SIEM as soon as they’re published.
Get matching new stories delivered to your team as they break — not the next morning.
Ask questions about this story and take action on the answers.
Related stories
Other stories Mallory is tracking that overlap on entities, sources, or topic labels.
Microsoft ships Windows 11 KB5083769 and KB5082052 with RDP and BitLocker fixes
Microsoft released mandatory Windows 11 cumulative updates **KB5083769** for versions **25H2/24H2** and **KB5082052** for **23H2**, delivering April Patch Tuesday security fixes alongside reliability and feature improvements. The `25H2` and `24H2` releases share the same changes because both are based on `24H2`, and the update moves those branches to builds **26200.8246** and **26100.8246**. Microsoft said the packages include protections against phishing through malicious **`.rdp`** files, Secure Boot certificate management improvements, and a fix for an issue that had pushed some systems into **BitLocker Recovery** after Secure Boot updates; the release also bundles servicing stack update **KB5088467**.
Apr 30, 2026
Windows 11 25H2/24H2 Preview Updates Add AI Features and Flag Secure Boot Certificate Expiration
Microsoft began rolling out **Windows 11 preview updates** for versions **25H2 and 24H2** (including the optional non-security preview update `KB5074105` and Release Preview builds `26200.7701`/`26100.7701`) focused on functionality, performance, and reliability improvements rather than patching new security vulnerabilities. The updates emphasize expanded **AI-driven experiences** (including refinements to Copilot+ PC-related models and more natural-language assistance within Settings), along with usability changes and a simplified Windows update title format intended to reduce administrative friction in tools like **WSUS** and **Microsoft Configuration Manager**. Alongside these feature updates, Microsoft highlighted an operational security risk: **Windows Secure Boot certificates** used by most Windows devices are expected to begin expiring in **June 2026**, and organizations that do not update Certificate Authority (CA) material in time may face devices that cannot boot securely. Separately, consumer guidance circulated on bypassing Windows 11 hardware eligibility checks (notably **TPM 2.0** requirements) to upgrade “unsupported” PCs; while this may extend device usability after Windows 10 support ended, it can also undermine Microsoft’s intended security baseline and increase enterprise risk if adopted outside controlled policy.
Mar 21, 2026
Microsoft March Patch Tuesday Ships 83 Fixes and Windows 11 Cumulative Updates
Microsoft’s March Patch Tuesday security release shipped fixes for **83 vulnerabilities** across its enterprise software and services, and was notable for having **no actively exploited zero-days** for the first time in six months. Microsoft flagged **six** vulnerabilities as “more likely to be exploited,” and noted two issues—`CVE-2026-21262` and `CVE-2026-26127`—were **publicly known** at release. Researchers highlighted an Excel information-disclosure issue, `CVE-2026-26144`, describing a scenario where an attacker could potentially induce a *Copilot Agent* to exfiltrate data in a **zero-click** style workflow, and also pointed to Office flaws `CVE-2026-26110` and `CVE-2026-26113` (CVSS 8.4) that could enable **arbitrary code execution** via the Office preview pane. Microsoft also released **mandatory Windows 11 cumulative updates** `KB5079473` (25H2/24H2) and `KB5078883` (23H2) that incorporate the March 2026 Patch Tuesday security fixes, along with additional non-security changes. The updates advance build numbers to **26200.8037/26100.8037** (25H2/24H2) and **22631.6783** (23H2), expand “high-confidence device targeting” to increase coverage for automatic delivery of new **Secure Boot certificates**, and include reliability improvements such as better File Explorer search across drives and changes to **Windows Defender Application Control (WDAC)** behavior for COM objects (policy listing support).
Mar 30, 2026