In the past few days, numerous reports on Reddit and Microsoft’s forums began pointing towards issues with Microsoft Defender that was causing users’ boot drives to fill up. While some users complained of small files less than 2KB in size causing minor problems, other reported seeing multiple gigabytes of storage hijacked by thousands of files in the Windows Defender folder. The files were showing up in the programData\Microsoft\Windows Defender\Scans\History\Store folder, causing massive backups as well.
Guessing from a long list of responses on multiple forum threads and on Reddit, the bug was affecting users running multiple security software on Windows Server 2016 and 2019. Some users reported being unable to open the folder itself, thanks to the boot drive filling up and causing slowdowns. While some admins suggested disabling real-time protection in Defender, others began sharing command-line scripts to delete files in the History folder.
A response on another Reddit thread from a user who raised the issue with Microsoft’s support teams suggests that the firm has acknowledged the issue and is already rolling out a fix for the problem. This was corroborated by another user’s comment on the support forums. The culprit supposedly is present in the Engine version 1.1.18100.5 and is being fixed with an update, bumping the version up to 1.1.18100.6. The update has begun propagating to users in the “normal release cycles” and will make it to mainstream users tomorrow, May 6, the user adds.
The bug has understandably been a frustrating one for system admins, thanks to the system slowdowns and backup issues caused to Windows Server users. If you have been facing this issue, it is best to check for updates in Windows Update to look for the fix.