Unknown Mozilla dev addon "Looking Glass 1.0.3" on browser

This is what it looks like: https://imgur.com/a/mriUw

It scared the hell out of me! Are these guys losing their minds?

It was reported as a bug and the response thus far is indeed underwhelming for such a severe issue: https://bugzilla.mozilla.org/show_bug.cgi?id=1424977

It wasn't supposed to be visible on the addons page

I don't think that makes it better. Knowing that there's a way to get an addon installed invisibly is going to be more justification for paranoia.

You can disable these studies under Options | Privacy and Security

I hate the fact that Firefox increasingly makes me jump through all sorts of hoops to find all the hidden options to turn off their various spyware attempts. Its the Win10 of browsers...

Going through your browser settings really is quite the hoop.

Yeah, its so intuitive for the average person to type: about:config in address bar and scroll through hundreds of oddly named parameters to turn off spyware.

Comments like yours are illustrative of a certain mindset. When you encounter the complexity of domains you are not intimately familiar with (court system, law, finance, etc), and those complexities are designed specifically to make it hard for you to protect yourself, I'm sure you are just as understanding as you are now.