A VideoStreamEncoder may have been freed in a race condition with VideoBroadcaster::AddOrUpdateSink, resulting in a use-after-free, memory corruption, and a potentially exploitable crash. This vulnerability affects Firefox < 78.
https://www.mozilla.org/security/advisories/mfsa2020-24/
https://security.gentoo.org/glsa/202007-10
https://bugzilla.mozilla.org/show_bug.cgi?id=1639734
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.html
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.html