October's update turned off the option to turn the security on
October 2026 update greys out Smart App Control's enable button
The market's verdict: -1.4% on MSFT in the week after.
What actually happened
The October 13, 2026 Patch Tuesday update greys out the On button for Smart App Control, so anyone who had the malware blocking feature switched off can no longer switch it back on through any supported interface. Microsoft's official workaround is hand-adding two registry keys, which is where consumer security features go to be quietly abandoned. A permanent fix is promised in a future update. Ten days before this site's deadline, the year provided its own closing argument.
This one is well documented.
Were you affected? Unbreak it
Microsoft's documented workaround: re-enable the button via two registry values
reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2883193997 /t REG_DWORD /d 1 /f reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2850574478 /t REG_DWORD /d 1 /f (Run both in an admin Command Prompt, reboot, and the On button returns. Delete the two values once a real fix ships.)
A proper fix is promised in a future update
Microsoft has acknowledged this issue; a fix ships in an out-of-band or next cumulative update. Check Windows Release Health before manual workarounds.
Links
-
Impact
- ZDNet (publication)
↳ caused by KB5127648
Timeline
- Oct 13, 2026 Mitigated Microsoft put safeguards around it.