Windows Defender bug causing Quick and Full scans to fail

What you need to know

  • The latest version of Windows Defender has a bug that causes Quick and Full scans to fail.
  • Real time scanning still works for Windows Defender despite the bug.
  • Microsoft confirmed that the company is working on a fix.

The latest version of Windows Defender has a bug that will cause Quick and Full scans to fail after only a few seconds and scanning only a small number of files (via ZDNet). The bug affects Windows Defender version 4.18.1908.7 and later. Several users reported the issue on Microsoft support forums (opens in new tab) as well as Reddit.

Windows Defender version 4.18.1908.7 was released earlier this week. The bug causing scans to fail was introduced while Microsoft attempted to fix a separate bug in the July 2019 Patch Tuesday update.

In addition to Windows Defender on Windows 10, the bug affects all versions of Windows Defender on all versions of Windows. As pointed out by ZDNet, the bug also affects Security Essentials (opens in new tab).

Microsoft confirmed to ZDNet that the company is working on a fix for the bug. Microsoft pointed out that real-time scanning protection still works despite the bug and that malware should be detected in real-time.

If you'd like to scan your system while the bug is still affecting Windows Defender, you can still perform a Custom scan with the tool.

Sean Endicott
News Writer and apps editor

Sean Endicott brings nearly a decade of experience covering Microsoft and Windows news to Windows Central. He joined our team in 2017 as an app reviewer and now heads up our day-to-day news coverage. If you have a news tip or an app to review, hit him up at (opens in new tab).