Security Vulnerabilities fixed in Thunderbird 102.2.1 — Mozilla

If a Thunderbird user replied to a crafted HTML email containing a meta tag, with the meta tag having the http-equiv=“refresh” attribute, and the content attribute specifying an URL, then Thunderbird started a network request to that URL, regardless of the configuration to block remote content. In combination with certain other HTML elements and attributes in the email, it was possible to execute JavaScript code included in the message in the context of the message compose document. The JavaScript code was able to perform actions including, but probably not limited to, read and modify the contents of the message compose document, including the quoted original message, which could potentially contain the decrypted plaintext of encrypted data in the crafted email. The contents could then be transmitted to the network, either to the URL specified in the META refresh tag, or to a different URL, as the JavaScript code could modify the URL specified in the document. This bug doesn’t affect users who have changed the default Message Body display setting to ‘simple html’ or ‘plain text’.
When receiving an HTML email that contained an iframe element, which used a srcdoc attribute to define the inner HTML document, remote objects specified in the nested document, for example images or videos, were not blocked. Rather, the network was accessed, the objects were loaded and displayed.
When receiving an HTML email that specified to load an iframe element from a remote location, a request to the remote document was sent. However, Thunderbird didn’t display the document.
Thunderbird users who use the Matrix chat protocol were vulnerable to a denial-of-service attack. An adversary sharing a room with a user had the ability to carry out an attack against affected clients, making it not show all of a user’s rooms or spaces and/or causing minor temporary corruption.