When a worker is shutdown, it was possible to cause script to run late in the lifecycle, at a point after where it should not be possible. This vulnerability affects Firefox < 96, Thunderbird < 91.6, and Firefox ESR < 91.6.
https://www.mozilla.org/security/advisories/mfsa2022-06/
https://www.mozilla.org/security/advisories/mfsa2022-05/