Mail Multiple Information Disclosure
As a privacy measure to prevent senders (primarily spammers) from tracking
when e-mail is read Thunderbird does not load remote content referenced from
an HTML mail message until a user tells it to do so. This normally includes
the content of frames and CSS files, but CrashFr showed it was possible to
bypass this restriction through indirection: the direct CSS or iframe src is
included in-line, with that including remote content.
Switch the "view message body as..." choice to "Simple HTML" or "Plain
text". Or for POP mail, after downloading the mail switch to offline mode
before reading any of it.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.