Microsoft has released the September cumulative update KB5124008 for Windows 11, which is considered the largest update for the OS in 2026. The update upgrades Windows 11 24H2 to build 26100.9445 and Windows 11 25H2 to build 26200.9445.
The update introduces the ability to move the taskbar to any of the four screen edges for the first time since the release of Windows 11 in 2021. Users can now also adjust the size of the Start menu and customize the visibility of recommended content and pinned applications.
Security improvements include 974 vulnerability fixes, with 723 patches targeting the Windows system. A new authentication mechanism requires Windows Hello verification for administrative tasks, and post-quantum ML-KEM algorithms are now supported for TLS key exchange.
Enterprise features have been expanded with the addition of Device Association in Windows Autopilot and Process Isolation for Microsoft Execution Containers. The latter is designed to restrict permissions for AI agents and automatically generated code.
The update removes the Windows Management Instrumentation Command-line utility (WMIC) from Windows 11 24H2 and 25H2. Additionally, users can now disable Bing and Microsoft Store search results to focus Windows Search exclusively on local content.
