CVE-2025-11711 is a vulnerability in Firefox and Thunderbird where some JavaScript Object properties that were intended to be non-writeable could be modified. This issue affects Firefox versions prior to 144 and Firefox ESR versions prior to 115.29 and 140.4, as well as Thunderbird versions prior to 144 and 140.4. The vulnerability was addressed in Firefox 144 and corresponding ESR and Thunderbird releases.