I noticed this problem when I implemented the Facebook Like Button plugin on my website, and got this error in my browser console:
Hmm, I'm assuming that Firefox is talking about the last request, which is to Facebook's API. But just to be sure...
Alright, I guess they just haven't gotten around to updating yet. But wait a minute, Facebook themselves are planning to block apps that use SHA-1 in about a month!
Hmm, maybe my browser is caching some old cert (is that even possible???) Well, let's see:
What the heck is going on here?