A process isolation vulnerability in Firefox stemmed from improper handling of javascript: URIs, which could allow content to execute in the top-level document's process instead of the intended frame, potentially enabling a sandbox escape. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Firefox ESR < 115.23, Thunderbird < 138, and Thunderbird ESR < 128.10.
https://www.mozilla.org/security/advisories/mfsa2025-32/
https://www.mozilla.org/security/advisories/mfsa2025-31/
https://www.mozilla.org/security/advisories/mfsa2025-30/
https://www.mozilla.org/security/advisories/mfsa2025-29/