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Microsoft fixes 5-year-old Windows Defender bug that was killing Firefox performance [TechSpot]
View Article on TechSpot
For more than five years, the troublesome security protection provided by Microsoft Defender was negatively affecting Firefox users during their web browsing sessions. The Antimalware Service Executable component of Defender (MsMpEng.exe) was acting strange, showing a high CPU usage when Firefox was running at the same time.