A use-after-free vulnerability exists in the Widget: Cocoa component of Mozilla Firefox. This memory corruption flaw affects Firefox versions prior to 149 and Firefox ESR versions prior to 140.9. The vulnerability is tracked as CVE-2026-4711 and has been documented in Mozilla's security advisories. Use-after-free vulnerabilities can potentially lead to arbitrary code execution or denial of service conditions. Mozilla has addressed this issue in the latest versions of both Firefox and Firefox ESR.