Short bio

PUM.Optional.FireFoxSecurityOverride is the detection for several potentially unwanted modifications (PUMs) in user.js, a Firefox browser configuration file, where the Safe Browsing feature is disabled or the viewing of mixed content is enabled in Firefox. As a result, users are made vulnerable to sites that may harbor insecure or potentially malicious content.

System modifications

The following strings are modified in user.js:

user_pref("browser.safebrowsing.enabled", true);

user_pref("browser.safebrowsing.enabled", false);

user_pref("browser.safebrowsing.malware.enabled", true);

user_pref("browser.safebrowsing.malware.enabled", false);

user_pref("browser.safebrowsing.downloads.enabled", true);

user_pref("browser.safebrowsing.downloads.enabled", false);

user_pref("security.mixed_content.block_active_content", true);

user_pref("security.mixed_content.block_active_content", false);


Malwarebytes automatically sets the values of the modified strings in user.js to “true” to stop triggering the detection of PUM.Optional.FireFoxSecurityOverride.

Add an exclusion

When 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.

Select your language