If you're an unpaid volunteer? Yeah - nah. They can tell you "Sorry, I'm playing with my cat for the next 3 months, maybe I'll get to it after that?", or just "Fuck off, I don't care."
(I'm now playing out a revenge fantasy in my head where the ffmpeg team does nothing, and Facebook or Palantir or someone similar get _deeply_ hacked via the exploit Google published and theat starts the planets biggest ever pointless lawyers-chasing-the-deepest-pockets fight.)
In this particular case it’s hardly obvious which patch you should submit. You could fix this particular bug (and leave in place the horrible clunky codec that nobody ever uses) OR you could just submit a patch that puts it behind a compile flag. This is really a decision for the maintainers, and submitting the latter (much better!) patch would not save the maintainers any meaningful amount of time anyway.
You can say publicly that “there is an ABC class vulnerability in XYZ component” so that users are aware of the risk.
This also informs users that it’s not safe to use ffmpeg or software derived from it to open untrusted files, and perhaps most importantly releasing this tells the distro package maintainers to disable the particular codec when packaging.
I don't understand how anyone believes that behavior is acceptable.