Only 2, which Mozilla installed and activated as a default:
Cisco's OpenH264 Video Codec
Google's Widevine Content Decryption Module
The OpenH264 codec shows it was updated on 24. May. That jibes with my suspicion that this has happened because of the latest Firefox updates. I find that little things break across the various websites I visit, as Mozilla pushes out Firefox updates.
FF is now up to release 67.0.2, and this particular bug persists. In Firefox, the text editor box is still disabled where it is presented. That goes for the main page of a post, as well as when I click the Reply link and open the full-page text editor.
I'm using Chrome right now, to write this reply.
If there are other features that aren't working in FF 67, I haven't found them yet.
This is the only forum I belong to built with XenForo, too; maybe this bug is specific to this version of Firefox and the web software.