Try disabling the WebProtect extension here:

orange Firefox button (or Tools menu) > Add-ons > Extensions category

If a link appears to restart Firefox, go ahead and do that to complete the process.

Also, I don't know what Plus-HD is. If that one isn't critical, you might want to disable that one, too.

Since different malware/spyware/adware scanners target different things, you might want to run some supplemental scans. These three tools are highly regarded (and free):

• Malwarebytes Anti-malware : http://www.malwarebytes.org/products/malwarebytes_free
• AdwCleaner : http://www.bleepingcomputer.com/download/adwcleaner/ (ignore banner ads for other products)
• SUPERAntiSpyware : http://www.superantispyware.com/

Your extensions list also shows a disabled TopArcades extension.

• [/questions/960863]

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.

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