Microsoft has released the Windows 10 KB5122878 extended security update, bringing September’s security fixes and a series of reliability changes to eligible devices.
The update is available to organisations running Windows 10 Enterprise LTSC and to devices covered by Microsoft’s Extended Security Updates (ESU) programme. Users can install it through Settings by opening Windows Update and selecting “Check for updates”.
What Windows 10 KB5122878 changes
KB5122878 updates standard Windows 10 installations to build 19045.7725, while Windows 10 Enterprise LTSC 2021 devices move to build 19044.7725.
Microsoft is no longer adding new features to Windows 10, so the package is focused on security, compatibility and bug fixes. It incorporates the wider September 2026 Patch Tuesday security updates, which addressed 966 vulnerabilities across Microsoft products, including two zero-day flaws reported as actively exploited.
The update expands the device-targeting data used to deliver new Secure Boot certificates automatically. Microsoft said certificate deployment through Windows Update would continue over the coming months on supported personal computers and non-managed business devices.
It also updates time-zone handling for Morocco, reflecting the country’s move to permanent UTC+00:00 from 20 September 2026. In addition, Microsoft has improved diagnostic logging for the OMA DM Client, providing more information when the component connects to a server.
Compatibility has been strengthened during the rotation of Windows certificate authorities. Windows Code Integrity policies will now recognise the Microsoft Windows Production PCA 2026 RSA2048-SHA256 certificate as equivalent to the earlier PCA 2011 certificate.
Other fixes address a Remote Desktop problem that could prevent redirected audio from playing on the local computer in some configurations. Microsoft has also resolved an issue in which devices with an unrecommended BitLocker Group Policy configuration could be prompted for their recovery key.
Microsoft has listed no known issues with Windows 10 KB5122878.
