Microsoft resolved an issue in its Windows Security framework that incorrectly indicated Microsoft Defender Antivirus was disabled. This fix was implemented through Defender platform update 4.18.26080.4, released on September 17. The update installs automatically unless users have blocked mandatory security updates. Users had been receiving false alerts during system boot and intermittently afterward, which redirected them to the Windows Security home tab where settings appeared normal. Microsoft acknowledged the issue on August 28, affecting all supported versions of Windows and Windows Server with the latest Defender updates, but did not specify the triggering update. Users in the Windows Insider program reported similar warnings as early as June.