Microsoft has released Windows 10 KB5099539, the July 2026 cumulative update that delivers security fixes for a record-breaking 570 vulnerabilities. The update also resolves several known issues affecting File Explorer, OLE Automation, Remote Desktop, and Secure Boot.
The update is available for Windows 10 Enterprise LTSC systems and consumer devices enrolled in Microsoft’s Extended Security Updates (ESU) program.
Microsoft Extends Windows 10 ESU Program
Microsoft originally planned to provide consumers with just one year of Extended Security Updates after Windows 10 reached the end of support.
However, the company recently expanded the free ESU program by another year. Eligible consumer devices can now continue receiving security updates until October 12, 2027, provided they are enrolled in the program.
Users running Windows 10 Enterprise LTSC or participating in ESU can install the latest update through Settings > Windows Update by selecting Check for updates.
After installation:
- Windows 10 updates to Build 19045.7548
- Windows 10 Enterprise LTSC 2021 updates to Build 19044.7548
July Update Focuses on Security and Stability
Microsoft is no longer adding new features to Windows 10. Instead, KB5099539 focuses on security improvements and bug fixes.
The update includes all security patches released during the July 2026 Patch Tuesday, which addressed 570 vulnerabilities, including:
- Two actively exploited vulnerabilities.
- One publicly disclosed zero-day vulnerability.
- Hundreds of additional security flaws across Windows components.
Known Issues Fixed in KB5099539
Microsoft also resolved several problems reported after previous updates.
OLE Automation Compatibility Restored
A compatibility issue introduced in the June 2026 update caused some applications using the IDispatch::Invoke method with BYREF parameters to fail.
KB5099539 corrects the memory handling behavior, restoring normal application functionality.
File Explorer and Recycle Bin Fixes
The update resolves an issue where the OneDrive shortcut stopped working when File Explorer was launched with administrator privileges.
Microsoft also fixed a bug that caused the Recycle Bin confirmation dialog to display an internal file name instead of the original file name during permanent deletion.
Keyboard Shortcut Improvements
Microsoft adjusted how Windows unregisters and cleans up hotkeys.
In rare cases, some built-in Windows features may temporarily stop responding to keyboard shortcuts after the update. Restarting the affected application usually resolves the problem.
Secure Boot and Remote Desktop Receive Security Improvements
KB5099539 introduces additional protections for Secure Boot and Remote Desktop.
For Secure Boot, Windows Security now provides dynamic status reporting and expands automatic deployment of updated Secure Boot certificates to more compatible devices.
The update also strengthens Remote Desktop security by adding support for SHA-2 certificate thumbprints for trusted RDP publishers. SHA-1 remains available only for compatibility and will eventually be removed.
Microsoft recommends administrators migrate to SHA-256 or stronger certificate algorithms as soon as possible.
Networking Change May Affect Legacy Applications
The update introduces a security hardening change that requires TDI transport registration.
Applications relying on unregistered third-party TDI transports may stop functioning after the update.
Administrators can determine whether their systems are affected by opening Event Viewer and checking the Windows System log for AFD Event ID 16003 entries. If the event reports an unregistered TDI provider, the affected transport must be updated or replaced.
No Other Known Issues Reported
Aside from the networking compatibility change affecting some legacy software, Microsoft says it is not aware of any additional known issues with Windows 10 KB5099539.
Organizations and consumers still running Windows 10 should install the update promptly to receive the latest security protections included in the July 2026 release.
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