When importing resources using Web Workers, error messages would distinguish the difference between `application/javascript` responses and non-script responses. This could have been abused to learn information cross-origin. This vulnerability affects Firefox < 126, Firefox ESR < 115.11, and Thunderbird < 115.11.
https://www.mozilla.org/security/advisories/mfsa2024-23/
https://www.mozilla.org/security/advisories/mfsa2024-22/
https://www.mozilla.org/security/advisories/mfsa2024-21/
https://lists.debian.org/debian-lts-announce/2024/05/msg00012.html
https://lists.debian.org/debian-lts-announce/2024/05/msg00010.html