Microsoft fixes high CPU usage bug in Windows Defender that impacts Firefox users

On April 4th, Microsoft released a patch as part of its March 2023 Engine Update, which should result in lower CPU usage when using Firefox on sites like YouTube. This patch was released in response to a bug found in Windows Defender which caused certain system calls to be expensive on CPU cycles when its Real-time Protection feature was enabled.

The bug was discovered by a Mozilla engineer, who reported it to Microsoft. It was found that when users were accessing certain websites, such as YouTube, the CPU usage would spike drastically and cause their computer to slow down. This issue was caused by the Windows Defender Real-time Protection feature, as it was making system calls which were expensive on CPU cycles.

The patch released by Microsoft should resolve this issue, and users should now experience lower CPU usage when using Firefox on sites like YouTube. It is important to note that this patch is only applicable to Windows Defender Real-time Protection, and not to any other security programs. It is also worth mentioning that the issue only affected Firefox, and not other browsers.

Overall, this patch should result in improved performance for Firefox users and ensure that they can browse the internet with peace of mind, knowing that their computer is safe and secure.