Microsoft has officially acknowledged a bug in the latest update for Defender Antivirus that triggers false error messages. Users on affected systems may see a notification stating that the antivirus software is turned off, even though the service continues to function correctly and remains enabled in the settings menu.
The issue primarily occurs during system startup, though Microsoft noted that the notification may appear intermittently at other times. Notably, the warning persists even for users who have previously disabled system notifications. The company confirmed that the core protection features are not actually impacted by this display error.
The bug affects a wide range of operating systems, including Windows 11 versions 26H1, 25H2, 24H2, and 23H2. Windows 10 users on versions 22H2, 21H2, and Enterprise LTSC editions from 2016 and 2019 are also experiencing these false alerts.
Server environments are similarly impacted by the update. The list of affected server software includes Windows Server 2025, 2022, 2019, 2016, 2012 R2, and 2012. Microsoft is currently addressing the reporting error across these platforms.
