I didn't install and run anything on your computer. I don't work for Mozilla.

And you installed a piece of open-source software whose source code you could have audited at any time, but you chose not to. You delegated the auditing to someone else, and now you're upset at what they chose to do with the power you gave them. You're free to complain that you don't like what they did, and not to trust them in the future, but you don't get to say that you had no chance to give input or to see what would run. You had plenty of opportunities for that and did not do it.