Microsoft warned that Windows’ built-in file history backup feature may stop working on some systems after installing the September 2026 security updates.
File History (introduced under Windows 8 and replaced by Windows Backup, which backs up data to OneDrive) automatically saves copies that allow users to restore accidentally deleted or corrupted files with an older version from hours, days, or weeks ago.
By default, File History backs up all folders in the user’s account profile (Documents, Music, Pictures, Videos, and Desktop) to an external hard drive, such as: B. a USB flash drive, or a network storage location (NAS).
In one Service warning Seen by BleepingComputer and first discovered by Microsoft MVP Susan Bradley, Microsoft says affected customers can see application crash events in Event Viewer pointing to FileHistory.exe and KERNELBASE.dll.
“After installing the September 2026 Windows Security Update (the original KBs listed above), some customers who use File History may not be able to create or update backups,” it said. “File History, available through Control Panel > System and Security > File History, is used to back up files to an external drive or network location.”
On affected devices, Windows may also incorrectly display a “Reconnect drive” message even if compatible backup drives are connected and working properly. Other symptoms include the “Last Backup” timestamp not being updated and previously backed up files displaying a “No previous version available” message.
Affected Windows versions include Windows 10 21H2 or later, Windows 10 Enterprise LTSC 2016/2019, and Windows 11 23H2 and later.
The September 2026 cumulative updates have been linked to several issues affecting personal and business Windows users.
A week ago, Microsoft released out-of-band updates to fix Remote Desktop Services bugs. Problems with Hyper-Vand USB audio issues triggered by this month’s security updates.
However, it was also confirmed that these emergency updates did not resolve all audio issues caused by the September 2026 updates and that a fix for the remaining issues is still being worked on.
Microsoft has also released a temporary workaround for a separate bug that prevents some Windows 11 users from logging in with valid domain credentials after installing the September updates.
