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Microsoft releases Windows 10 KB5122878 extended security update

Recorded: Sept. 8, 2026, 7:01 p.m.

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Microsoft releases Windows 10 KB5122878 extended security update

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HomeNewsMicrosoftMicrosoft releases Windows 10 KB5122878 extended security update

Microsoft releases Windows 10 KB5122878 extended security update

By Lawrence Abrams

September 8, 2026
02:49 PM
0

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 updateSource: 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.

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Related Articles:
Microsoft releases Windows 10 KB5099539 extended security updateMicrosoft September 2026 Patch Tuesday fixes 966 flaws, 2 zero-daysMicrosoft August 2026 Patch Tuesday fixes 400 flaws, 3 zero-daysMicrosoft releases Windows 10 KB5120249 extended security updateMicrosoft July 2026 Patch Tuesday fixes massive 570 flaws, 3 zero-days

Cumulative Update
Extended Security Updates
KB5122878
Microsoft
Patch Tuesday
Security Update
Windows 10
Windows Update

Lawrence Abrams
Lawrence Abrams is the owner and Editor in Chief of BleepingComputer.com. Lawrence's area of expertise includes Windows, malware removal, and computer forensics. Lawrence Abrams is a co-author of the Winternals Defragmentation, Recovery, and Administration Field Guide and the technical editor for Rootkits for Dummies.

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Microsoft has released the Windows 10 KB5122878 extended security update, which incorporates the fixes from the September 2026 Patch Tuesday and addresses several bug issues. This update serves primarily as a delivery mechanism for critical security enhancements and bug resolutions. Installation procedures vary slightly depending on the system configuration; users running Windows 10 Enterprise LTSC or those enrolled in the Extended Security Update program can install this update through the standard Settings menu by manually checking for updates. Upon installation, Windows 10 will be updated to build 19045.7725, and Windows 10 Enterprise LTSC 2021 will be updated to build 19044.7725.

The core content of the KB5122878 update is centered on security patches and bug fixes rather than introducing new features. A significant component of this release involves addressing a record-breaking set of flaws identified during the September 2026 Patch Tuesday, which fixed 966 vulnerabilities across Microsoft products, including two zero-day flaws that were actively being exploited. Specific technical improvements within the update include enhancements to Secure Boot, which increases the confidence level for device targeting data and expands coverage for devices eligible to automatically receive new Secure Boot certificates; this process contributes to ongoing certificate deployment across supported PCs and non-managed business devices. Furthermore, the update addresses a time synchronization issue by adjusting Morocco Standard Time to reflect its transition to permanent UTC+00:00, effective September 20, 2026.

Other specific fixes detailed in the update involve system protocols and policies. The update improves the logging capabilities of the OMA DM Client component by saving more debug information when connecting to a server. Regarding application compatibility, the update refines Windows Code Integrity policies to improve application compatibility during the rotation of certificate authorities by recognizing Microsoft Windows Production PCA 2026 RSA2048-SHA256 as equivalent to PCA 2011. Additionally, the patch resolves an issue affecting Remote Desktop functionality related to audio redirection, ensuring that audio from remote sessions is correctly played on the local computer in various configurations. Finally, KB5122878 mitigates a known instability concerning BitLocker Group Policy, resolving an issue where devices with unrecommended BitLocker Group Policy configurations might require the entry of their recovery key. The author Lawrence Abrams, who is the owner and Editor in Chief of BleepingComputer.com, reported on these updates.