Microsoft admits September update broke Windows 11 File History, fix is optional

The September 2026 security update KB5124008 broke File History backups in Windows 11, preventing users from creating or updating backups to external drives. A fix is included in an optional preview of the October update, though issues with the 'Run now' option and save-time synchronization reportedly persist.

• September patch KB5124008 broke File History backup creation and updates
• Fix ships only in the optional October preview update
• Issues with 'Run now' and save-time sync reportedly remain
• Stable Windows 11 update expected on October 13