Re: "A few days ago, I fired up YT in Firefox and it disabled all my extensions."
I'm skeptical. If this happened, then we should all smash our devices and run for the hills in tinfoil hats because all bets are off.
I don't question your personal experience, I just question the fundamental cause. If YT – or indeed any website – can mess with a browser's extensions in that way, then something is seriously wrong with the browser. Mayhap you should check for malware?