Stefan Mileschin

Firefox provides several ways for other programs on your computer to install Firefox extensions, sometimes without your explicit consent. While you can disable these extensions, you often can’t uninstall them via Firefox’s Add-ons screen.

Mozilla has become more vigilant in protecting users and now asks you whether you want to enable such extensions after they’re installed. However, a disabled extension continues to clutter your list of installed extensions.

http://www.howtogeek.com/140448/how-...fox-extension/