Finally, thunderbird is secured for regular sarge users. See the DSA 781-1 announcement on details what is fixed and how to upgrade.
I am sorry for the delay on this, but as mentioned before we are working on a procedure to provide security for mozilla apps in a more timely manner.
Nevertheless, you can add my security archive to your sources.list.
If you want the lastest thunderbird and don’t mind that more than just thunderbird gets upgraded if a new thunderbird lands, use my stable backport archive instead.
If you want to send someone a human readable link to my archives, use this one: http://www.asoftsite.org/apt-archives.html.
Stay tuned!