April's update broke the backup software, guarding your files from being saved
April 2026 update broke third-party backup products via VSS timeouts
The market's verdict: +8.8% on MSFT in the week after.
What actually happened
The April 2026 cumulative update broke third party backup software from Acronis, Macrium Reflect, NinjaOne and others on Windows 11 Home and Pro, with VSS snapshot creation timing out, some machines silently dropping off their management consoles, and backups quietly failing. On May 4 Microsoft confirmed the cause: a vulnerable driver blocklist update that took the backup engines out with it. A security fix that stops backups is a bold strategy, roughly the firewall equivalent of removing the door.
This one is officially acknowledged.
Were you affected? Unbreak it
Uninstall the April update until backups work ↗
wusa /uninstall /kb:5083769 /quiet /norestart
Links
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Impact
- BleepingComputer (publication)
↳ caused by KB5083769
Timeline
- Apr 14, 2026 Confirmed First reports came in.
- May 4, 2026 Mitigated Cause confirmed as a driver blocklist update; fixes followed.