Package Instance

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.

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.

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.