Microsoft releases Windows 10 KB5122878 extended security update

Microsoft has released the Windows 10 KB5122878 extended security update, which includes this month's record-breaking September 2026 Patch Tuesday fixes, along with a few bug fixes.

If you are running Windows 10 Enterprise LTSC or are enrolled in the ESU program, you can install this update like normal by going into Settings, clicking on Windows Update, and manually performing a 'Check for Updates.'

Windows 10 KB5122878 update
Source: BleepingComputer

After installing this update, Windows 10 will be updated to build 19045.7725, and Windows 10 Enterprise LTSC 2021 will be updated to build 19044.7725.

What's new in Windows 10 KB5122878

Microsoft is no longer releasing new features for Windows 10, and the KB5122878 update primarily contains security updates and bug fixes.

The update also includes fixes released as part of today's record-breaking September 2026 Patch Tuesday, which fixed a massive 966 vulnerabilities across Microsoft's products, including two actively exploited zero-day flaws.

The complete list of fixes in KB5122878 is listed below:

• [Secure Boot] This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months.

• [Date and Time] This update adjusts Morocco Standard Time to reflect Morocco's transition to permanent UTC+00:00 effective September 20, 2026. This change ensures that the correct local time is displayed after the transition.

• [OMA DM protocol] This update improves the logging features of the OMA DM Client (omadmclient.exe) component. More debug information is now saved when connecting to a server.

• [Windows Code Integrity policies] Improves application compatibility during Windows certificate-authority rotation by recognizing Microsoft Windows Production PCA 2026 RSA2048-SHA256 as equivalent to PCA 2011.

• [Remote Desktop] This update addresses an issue that affects Remote Desktop audio redirection. Audio from the remote session might not play on the local computer in certain configurations.

• [BitLocker Group Policy] This update addresses the "Devices with an unrecommended BitLocker Group Policy configuration might be required to enter their BitLocker recovery key" known issue.

Microsoft says there are no known issues with this update.