Race conditions in reference counting code were found through code inspection. These could have resulted in potentially exploitable use-after-free vulnerabilities. This vulnerability affects Firefox < 116, Firefox ESR < 102.14, and Firefox ESR < 115.1.
https://www.mozilla.org/security/advisories/mfsa2023-31/
https://www.mozilla.org/security/advisories/mfsa2023-30/
https://www.mozilla.org/security/advisories/mfsa2023-29/
https://www.debian.org/security/2023/dsa-5469
https://www.debian.org/security/2023/dsa-5464
https://lists.debian.org/debian-lts-announce/2023/08/msg00010.html
https://lists.debian.org/debian-lts-announce/2023/08/msg00008.html