An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object. This vulnerability affects Firefox < 138.0.4, Firefox ESR < 128.10.1, Firefox ESR < 115.23.1, Thunderbird < 128.10.2, and Thunderbird < 138.0.2.

An attacker was able to perform an out-of-bounds read or write on a JavaScript object by confusing array index sizes. This vulnerability affects Firefox < 138.0.4, Firefox ESR < 128.10.1, Firefox ESR < 115.23.1, Thunderbird < 128.10.2, and Thunderbird < 138.0.2.

Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid From address to be used. For example, if the From header contains an (invalid) value "Spoofed Name ", Thunderbird treats spoofed@example.com as the actual address. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.

A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can be abused to fill the disk with garbage data, such as using /dev/urandom on Linux, or to leak Windows credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML mode is enough to load external content.

Thunderbird's handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript execution as part of the HTML. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.

It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to open the attachment, Thunderbird automatically accessed the link. The configuration to block remote content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in the X-Mozilla-External-Attachment-URL header of an email. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.

Error handling for script execution was incorrectly isolated from web content, which could have allowed cross-origin leak attacks. This vulnerability affects Firefox < 139, Firefox ESR < 115.24, Firefox ESR < 128.11, Thunderbird < 139, and Thunderbird < 128.11.

Due to insufficient escaping of the newline character in the “Copy as cURL” feature, an attacker could trick a user into using this command, potentially leading to local code execution on the user's system. This vulnerability affects Firefox < 139, Firefox ESR < 115.24, Firefox ESR < 128.11, Thunderbird < 139, and Thunderbird < 128.11.

Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability affects Firefox < 139, Firefox ESR < 128.11, Thunderbird < 139, and Thunderbird < 128.11.

A clickjacking vulnerability could have been used to trick a user into leaking saved payment card details to a malicious page. This vulnerability affects Firefox < 139, Firefox ESR < 128.11, Thunderbird < 139, and Thunderbird < 128.11.

Memory safety bugs present in Firefox 138, Thunderbird 138, Firefox ESR 128.10, and Thunderbird 128.10. 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. This vulnerability affects Firefox < 139, Firefox ESR < 128.11, Thunderbird < 139, and Thunderbird < 128.11.

Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 128.11 and Thunderbird < 128.11.