It was possible for a web extension with minimal permissions to create a `StreamFilter` which could be used to read and modify the response body of requests on any site. This vulnerability affects Firefox < 129, Firefox ESR < 115.14, Firefox ESR < 128.1, Thunderbird < 128.1, and Thunderbird < 115.14.
https://www.mozilla.org/security/advisories/mfsa2024-38/
https://www.mozilla.org/security/advisories/mfsa2024-37/
https://www.mozilla.org/security/advisories/mfsa2024-35/
https://www.mozilla.org/security/advisories/mfsa2024-34/