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Microsoft fixes bug behind ‘Defender Antivirus is turned off’ alerts

September 18, 2026 · BleepingComputer · Severity: MEDIUM

Microsoft has resolved a known issue that causes incorrect alerts warning that Defender Antivirus was turned off after installing recent updates.

Key Takeaways

  • Microsoft has resolved a known issue that caused incorrect alerts warning users that Defender Antivirus had been turned off after installing recent Windows security updates, restoring proper status reporting.
  • The bug, which affected enterprise and consumer Windows devices alike, generated false positive alerts that could have led to unnecessary support tickets and confusion about the actual security state of affected systems.
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