Microsoft’s October update for Windows 11 has a side effect worth knowing about. After installing update KB5127648, released on 13 October for Windows 11 versions 24H2, 25H2 and 26H2, some users find they can no longer switch on a security feature called Smart App Control. The option simply appears greyed out.
What is Smart App Control?
Smart App Control is a built-in Windows protection that checks programs before they run. It uses Microsoft’s cloud service to spot apps that are malicious, compromised or otherwise suspicious, and stops them from running. For a small business without dedicated security staff, it is one more layer between a staff member and a dodgy download.
Who is affected?
According to Microsoft, as reported by PCWorld, only PCs where Smart App Control was already turned off are affected. The problem is for anyone who had it off and now wants to turn it on, for example after setting up a new machine or tightening security.
The update itself fixes other problems, including mouse glitches in games and black screens after logging on, so it is not a reason to avoid updating. Keep installing Windows updates.
Is there a fix?
ZDNet reports that a change in the Windows Registry gets around the bug. The Registry controls how Windows behaves, and a wrong edit there can cause real problems, so this is a job for whoever looks after your IT rather than something to try from a forum post.
What should you do?
- Check whether Smart App Control is on: open Windows Security, then App and browser control.
- If it is on, no action is needed.
- If it is off and greyed out, ask your IT provider to apply the workaround or confirm you have other protection in place.
- Keep Windows updates running on every work PC.
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