Mozilla Thunderbird is a standalone mail and newsgroup client. This update upgrades Thunderbird to version 91.9.0. Security Fix: * Mozilla: Bypassing permission prompt in nested browsing contexts * Mozilla: iframe Sandbox bypass * Mozilla: Fullscreen notification bypass using popups * Mozilla: Leaking browser history with CSS variables * Mozilla: Memory safety bugs fixed in Firefox 100 and Firefox ESR 91.9 * Mozilla: Reader mode bypassed SameSite cookies * Mozilla: Speech Synthesis feature not properly disabled * Mozilla: Incorrect security status shown after viewing an attached email For more details about the security issue, including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page listed in the References section.