Microsoft Defender Bug Triggers False Antivirus Off Alerts

A widespread bug in recent Microsoft Defender Antivirus updates is causing Windows users to receive false alerts claiming their antivirus software is turned off, even though it remains fully functional. Microsoft confirmed the issue on Friday, August 28, 2026, and stated it is working on a fix to be released in a future update. The erroneous notifications appear in the Windows Security app and can trigger when Windows starts or intermittently afterward. They persist even if notification settings are turned off.