
According to Juglaret, this is not the case as the 75% reduction percentage in CPU resource use is only taking into account the MsMpEng service and does not apply to global usage. Update: Mozilla engineer Yannis Juglaret, who isolated and worked on this bug, has shared additional context and details regarding the issue since some other news outlets were apparently sharing incorrect information that the global CPU usage would be reduced by 75%. Perhaps we will see such performance improvements in upcoming browser updates and it won't just be exclusive to Microsoft Defender alone. Interestingly, it has also been found that there is further scope of improvements to the processor usage in Firefox when compared to Chrome.

This includes even Windows 7 and 8.1 users, even though these platforms should not have had the performance issue with Firefox in the first place because the ETW events that cause it do not exist on these older versions of Windows. According to Microsoft, this will be deployed to all users as part of regular definition updates, which are packaged independently from OS updates.
