An attacker could, via a specially crafted multipart response, execute arbitrary JavaScript under the `resource://pdf.js` origin. This could allow them to access cross-origin PDF content. This access is limited to "same site" documents by the Site Isolation feature on desktop clients, but full cross-origin access is possible on Android versions. This vulnerability affects Firefox < 131, Firefox ESR < 128.3, Firefox ESR < 115.16, Thunderbird < 128.3, and Thunderbird < 131.
https://www.mozilla.org/security/advisories/mfsa2024-50/
https://www.mozilla.org/security/advisories/mfsa2024-49/
https://www.mozilla.org/security/advisories/mfsa2024-48/
https://www.mozilla.org/security/advisories/mfsa2024-47/