After installing the latest Defender Antivirus update for Windows 11, users are reporting notifications stating "Microsoft Defender Antivirus is turned off," despite protection working correctly. The false warnings typically appear during or immediately after booting up the system. Notably, these notifications surface even when notification settings are disabled, and all versions of Windows and Windows Server are affected.

Many TechPowerUp staff members experienced the error firsthand, confirming the widespread nature of the issue. The problem emerged with Platform number 4.18.26080.3, Engine version 1.1.26080.3, and Security intelligence number 1.1.159.11.0.

Microsoft acknowledged the issue, stating: "We are working to release a resolution in a future Microsoft Defender Antivirus update and will provide more information when it is available." The company noted that recent security enhancements and increased scanning capabilities inadvertently affected notification settings. Users are advised to check for updates in the coming weeks, as Microsoft continues addressing hundreds of AI-discovered vulnerabilities while improving threat detection.