PUM.Optional.Firefox LockedProxy

detection icon

Short bio

PUM.Optional.FirefoxLockedProxy is Malwarebytes’ detection name for a potentially unwanted modification that locks a proxy setting in the Firefox configuration file.

System modifications

In the Firefox configuration file which is usually located at %PROGRAMFILES%\Mozilla Firefox\mozilla.cfg on Windows machines, an entry is found for the network.proxy.type in the lockPref section.


Malwarebytes automatically removes the proxy.type entry to stop triggering the detection of PUM.Optional.FirefoxLockedProxy.

Add an exclusion

When a Potentially Unwanted Modification (PUM) is detected on your computer, Malwarebytes for Windows does not know whether 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 by design. To have Malwarebytes for Windows ignore a PUM, you must add the PUM to the Allow list. Here’s how to do it.

  1. When a PUM appears in the list of Scan results.
  2. Uncheck the entry or entries related to the PUM.
  3. Then click on Next.
  4. You will see a prompt giving you several options.
  5. Choosing Always ignore will add the PUM to the Allow List.
  6. You can remove them there when you decide they should no longer be ignored.
  7. When the PUM is on the Allow list it will no longer show up in your Scan results.