IIRC I remember seeing something in a forum that it is widevine, and that it had already worked in FF since whichever release included it (1-3 releases ago) if

IIRC I remember seeing something in a forum that it is widevine, and that it had already worked in FF since whichever release included it (1-3 releases ago) if the UA was spoofed, but this could be somone's failed test and a bad memory..