Security Vulnerabilities fixed in Thunderbird 91.10 — Mozilla

A malicious website could have learned the size of a cross-origin resource that supported Range requests.
A malicious webpage could have caused an out-of-bounds write in WebGL, leading to memory corruption and a potentially exploitable crash.
When exiting fullscreen mode, an iframe could have confused the browser about the current state of fullscreen, resulting in potential user confusion or spoofing attacks.
When downloading files on Windows, the % character was not escaped, which could have lead to a download incorrectly being saved to attacker-influenced paths that used variables such as %HOMEPATH% or %APPDATA%.This bug only affects Thunderbird for Windows. Other operating systems are unaffected.
On arm64, WASM code could have resulted in incorrect assembly generation leading to a register allocation problem, and a potentially exploitable crash.
A crafted CMS message could have been processed incorrectly, leading to an invalid memory read, and potentially further memory corruption.
When displaying the sender of an email, and the sender name contained the Braille Pattern Blank space character multiple times, Thunderbird would have displayed all the spaces. This could have been used by an attacker to send an email message with the attacker’s digital signature, that was shown with an arbitrary sender email address chosen by the attacker. If the sender name started with a false email address, followed by many Braille space characters, the attacker’s email address was not visible. Because Thunderbird compared the invisible sender address with the signature’s email address, if the signing key or certificate was accepted by Thunderbird, the email was shown as having a valid digital signature.
An attacker could have exploited a timing attack by sending a large number of allowCredential entries and detecting the difference between invalid key handles and cross-origin key handles. This could have led to cross-origin account linking in violation of WebAuthn goals.
Mozilla developers Andrew McCreight, Nicolas B. Pierron, and the Mozilla Fuzzing Team reported memory safety bugs present in Thunderbird 91.9. 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.