hello patchf, you may have malicious addons present. please try these steps:

1. reset firefox (this wil keep your bookmarks and passwords)
2. afterwards go to firefox > addons > extensions and in case there are still extensions listed there, disable them.
3. finally run a full scan of your system with different security tools like the free version of malwarebytes and adwcleaner to make sure that adware isn't present in other places of your system as well.

Troubleshoot Firefox issues caused by malware

Note that your System Details List shows that you have a user.js file in the profile folder to initialize some prefs on each start of Firefox.

The user.js file is only present if you or other software has created it, so normally it wouldn't be there. you can check its content with a plain text editor if you didn't create this file yourself.

The user.js file is read each time you start Firefox and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

Rename or delete the prefs.js file and possible numbered prefs-##.js and user.js files to reset all prefs to the default value.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences