If you want to avoid running random experimental mozilla code on your machine without any kind of confirmation needed by you remember to go to about:preferences

If you want to avoid running random experimental mozilla code on your machine without any kind of confirmation needed by you remember to go to about:preferences#privacy in the "Firefox Data Collection and Use" and turn "Allow Firefox to install and run studies" to off. I would also set the about:config options "network.allow-experiments" and "app.normandy.enabled" to false.