If you recently updated your PC and noticed your mouse pointer behaving erratically or Windows throwing scary security pop-ups, you are not alone. Microsoft has officially acknowledged two distinct regressions tied to recent Windows updates, with cumulative update KB5120998 (OS Build 26100.9278) right at the center of the disruption.
As Microsoft continues rolling out fresh features across Windows 11 news and updates, recent maintenance patches have brought unexpected UI glitches and notification errors. Here is a breakdown of what is going wrong, why it is happening, and how to handle it on your system.
1. KB5120998 Mouse Cursor Glitch: Custom Schemes Overwritten
Following the release of KB5120998, users started reporting that their mouse pointer customizations were disappearing after restarts or system boots.
Default Pointer Overrides: Custom cursor schemes, animated pointers, and High-DPI mouse cursors are automatically replaced with oversized, standard white pointers.
Customizations Won’t Stick: Attempts to restore custom mouse themes via Windows Settings or the legacy Control Panel fail, as the system immediately reverts to standard settings.
Affected OS Builds: The regression specifically impacts devices running Windows 11 builds updated with KB5120998 (OS Build 26100.9278 and later).
Current Status: Microsoft has opened an active investigation to determine why display scaling and personalization parameters are being overwritten.
2. False “Microsoft Defender Antivirus is Turned Off” Alerts
In addition to the KB5120998 cursor regression, Microsoft confirmed a separate notification glitch tied to recent security definition packages.
The Symptom: Pop-up warnings claim that “Microsoft Defender Antivirus is turned off,” even though real-time protection is active and fully functional inside the Windows Security panel.
Persistent Behavior: The warning appears upon booting into Windows and pops up intermittently during regular use. Muting system notifications does not suppress the alert.
Is Your PC Safe? Yes. Microsoft confirmed this is entirely a cosmetic error. Your system’s real-time security scanning remains fully operational in the background.
Affected Systems: This issue impacts multiple versions of Windows 11, Windows 10, and Windows Server running the latest Defender updates.
What Should You Do Right Now?
If these update bugs are interfering with your workflow, here are the best steps to take while Microsoft prepares official patches:
Uninstall KB5120998 (If Cursors Are Broken): Because KB5120998 is an optional update, you can safely remove it to restore your mouse setup. Go to Settings > Windows Update > Update History > Uninstall Updates, locate KB5120998, and click Uninstall.
Ignore the Security Pop-ups: Do not reinstall third-party antivirus software or alter system settings. Microsoft will resolve the false Defender alarm automatically through an upcoming background definition update.
Submit System Diagnostic Logs: If you prefer to keep KB5120998 installed to test other performance updates, press Windows key + F to open the Feedback Hub and submit a bug report directly to Microsoft’s engineering team.
Stay tuned to WinCentral’s Windows 11 coverage for further updates, patch releases, and fixes as Microsoft rolls out solutions for these issues.
