Security Vulnerabilities fixed in Thunderbird 115.12 — Mozilla

Memory corruption in the networking stack could have led to a potentially exploitable crash.
If a garbage collection was triggered at the right time, a use-after-free could have occurred during object transplant.
By monitoring the time certain operations take, an attacker could have guessed which external protocol handlers were functional on a user’s system.
By tricking the browser with a X-Frame-Options header, a sandboxed iframe could have presented a button that, if clicked by a user, would bypass restrictions to open a new window.
On Windows 10, when using the ‘Save As’ functionality, an attacker could have tricked the browser into saving the file with a disallowed extension such as .url by including an invalid character in the extension. Note: This issue only affected Windows operating systems. Other operating systems are unaffected.
Offscreen Canvas did not properly track cross-origin tainting, which could be used to access image data from another site in violation of same-origin policy.
By manipulating the text in an tag, an attacker could have caused corrupt memory leading to a potentially exploitable crash.
Memory safety bugs present in Firefox 126, Firefox ESR 115.11, and Thunderbird 115.11. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.