Short bio

This detection is for several potentially unwanted modifications (PUMs) on user.js, a Firefox browser configuration file, where the installation of any third-party add-on or extension to Firefox is allowed.

System modifications

The following string is modified in user.js:

user_pref("extensions.autoDisableScopes", 15);

user_pref("extensions.autoDisableScopes", 14);
user_pref("extensions.autoDisableScopes", 0);


Malwarebytes automatically deletes the user.js file that triggers the detection of PUM.Optional.FireFoxSearchOverride. Also, we advise users to do a full system scan as PUM.Optional.FireFoxSearchOverride could have been added to the system by malware or PUP.

Add an exclusion

When a PUM is detected on your computer, Malwarebytes for Windows does not know if it was authorized. Optimization software, malware, and Potentially Unwanted Programs (PUPs) are known to make these types of changes, hence they are regarded as potentially unwanted.

To have Malwarebytes for Windows ignore a PUM, you must add the PUM as an exclusion.

  1. Open Malwarebytes for Windows.
  2. Click Settings, then click the Protection tab.
  3. Scroll down to the bottom.
  4. Turn off Automatically quarantine detected malware.Turning this setting off prevents Malwarebytes for Windows from quarantining the PUM automatically.
  5. Go to the Dashboard, then click Scan Now.
  6. When the Threat Scan Results appear, uncheck the box next to the detected PUM you want to keep.
  7. Click Next.
  8. On the Remaining Items window, click Ignore Always to add the exclude the detected PUM(s).
  9. Turn on Automatically quarantine detected malware.To find this setting, click Settings > Protection.

When a PUM is excluded, Malwarebytes for Windows does not detect the PUM during scans or Real-Time Protection.

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