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Microsoft Fixes False Alerts That Defender Antivirus Was Turned Off

· Original article ↗

Summary

Microsoft fixed an issue that falsely warned Windows users that Defender Antivirus was off. The fix is in update version 4.18.26080.4, released September 17, and applies to supported Windows client and server versions.

Key points

  • Windows Security could repeatedly report that Defender Antivirus was turned off even while it was functioning and enabled.
  • The issue affected supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025.
  • Microsoft resolved the issue in Defender Antivirus update version 4.18.26080.4, released September 17.
  • The issue had affected Windows Insider Release Preview users since at least June; Microsoft acknowledged it in late August.

Article Details

Event Type
Microsoft resolved a software issue causing Windows Security to falsely report that Microsoft Defender Antivirus was turned off after recent updates.
Impact
The false alerts affected supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025. They could recur at startup and intermittently afterward, prompting users to turn on antivirus that was already functioning correctly. Microsoft fixed the issue in Microsoft Defender Antivirus update version 4.18.26080.4, released September 17.

Vendors

MicrosoftMicrosoft has fixed a known issue that caused Windows Security to wrongly report that Microsoft Defender Antivirus was turned off after recent updates.

Products

Microsoft Defender AntivirusMicrosoft has fixed a known issue that caused Windows Security to wrongly report that Microsoft Defender Antivirus was turned off after recent updates.Windows 11The bug affected supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025, and was resolved in Defender Antivirus update version 4.18.26080.4 released on September 17.Windows SecurityMicrosoft has fixed a known issue that caused Windows Security to wrongly report that Microsoft Defender Antivirus was turned off after recent updates.Windows Server 2025The bug affected supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025, and was resolved in Defender Antivirus update version 4.18.26080.4 released on September 17.

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