Microsoft patches Windows Defender bug with the latest update

Just a couple of days back we covered a bug that caused Windows Defender to skip some items during an antivirus scan. While Microsoft didn’t officially acknowledge the issue, the company has issued a new update which fixes the bug.

Today, Microsoft has released KB4052623 update along with Security Intelligence Update for Windows Defender (v4.18.2003.8) which fixes the scanning issue for all the Windows 10 users. KB4052623 is currently available for Windows 10 Home, Pro and Enterprise users. Unfortunately, the update comes with a couple of known issues which might affect some users.

Known issues:

• New file pathBecause of a change in the file path location in the update, many downloads are blocked when AppLocker is enabled.
  To work around this issue, open Group Policy, and then change the setting to Allow for the following path:

  %OSDrive%\ProgramData\Microsoft\Windows Defender\Platform\*

• Secure Boot issue in version 4.18.1901.7 Some devices that are running Windows 10 do not start if they have Secure Boot turned on.

  We are working on this issue and plan to provide a fix in a future update. To work around this issue in the meantime, follow these steps:

  1. Restart the device, and enter the BIOS.
  2. Turn off Secure Boot, and then restart the device again.
  3. In an administrative Command Prompt window, run the following command:

     "%programdata%\Microsoft\Windows Defender\Platform\4.18.1901-7\MpCmdRun.exe" -revertplatform

  4. Wait for one minute, and then do the following:
     • Run sc query windefend to verify that the Windows Defender service is running.
     • Run sc qc windefend to verify that the Windows Defender binary no longer points to version 4.18.1901.7.

  5. Restart the device, re-enter the BIOS, and then turn on Secure Boot.

The new update is available through Windows Update and WSUS. Alternatively, users can also download the new update from Microsoft Update Catalog and install it manually.