And it would be a shame if Firefox didn't implement something, even so minor like a new version number, 'just' because sites break. You are Mozilla, send them a mail and give them a week to fix it, because you are f'ing Mozilla. I'm glad this is apparently just what they did here.
(Same thing when NVIDIA or Microsoft do contortions to support broken games. You already fixed the function or shader; don't hotpatch it but send it to the vendor and tell them to merge it or else...)