Unknown Mozilla dev addon "Looking Glass 1.0.3" on browser

What the fuck Mozilla? You can't just sideload extensions that are literally ads. There is no universe in which this is even a little bit okay.

http://qutebrowser.org/

And this is exactly what I'm going to do, switch to a simple browser, in my personal computers. If they programmed firefox to be capable of doing thinks like this, then definitely I cannot trust them anymore.