This is the best fix for Firefox, this updates you to the new version, and it works a treat. I installed this, and all of my addons are back, even uBlock Origin and Greasemonkey. So the incompetent Mozilla developers only took 9 hours to fix such a simple problem, the future is very bleak indeed. I hope this does not happen again though. I would hate to be using Youtube without uBlock origin. It is very painful waiting for the ads to finish before watching a video. I just want to listen to some nice music. But this is a fix that works, better late than never. I hope this is a lesson for them, judging by the level of hate directed at them on r/rfirefox/. I would hate to go through that.
Download the fixed version of Firefox on the Mozilla FTP site: https://ftp.mozilla.org/pub/firefox/candidates/66.0.4-candidates/build1/.