Windows Defender update limited scans to just about 40 files

After the recent string of bugs introduced by Windows 10 updates, there's now also an update that made Windows Defender go haywire. A couple of days ago, Microsoft published version 4.18.1908.7 of the anti-virus tool and messages soon appeared on online boards from users who noticed that the software scanned only about 40 files when you perform a full or quick scan.

BleepingComputer tested and confirmed the issue:

BleepingComputer has been able to independently confirm that this is happening on our own computers that have version 4.18.1908.7 (KB4052623) installed. [... W]hen we performed a Full scan, it only scanned 44 files and lasted 9 seconds.

Microsoft has already resolve the issue and pushed out Security Intelligence Update for Windows Defender Antivirus - KB2267602 (Version 1.301.1684.0). Apparently, there was a problem in the anti-virus definition. Microsoft says the issue did not affect real-time scanning, only manual scans were affected.