No, it's not just you.
As of a few hours ago a cert built into Firefox that handles extensions (which are all signed now) expired (doh!!) causing Firefox to complain to everyone their extensions are at risk or disabled.
https://news.slashdot.org/story/19/05/04/0457201/a-glitch-is-breaking-all-fi...
Let's see how fast the distros get a patched version from upstream to fix this...
Letting your cert expire... not one of Mozilla's brightest moments.