Mozilla Thunderbird is a standalone mail and newsgroup client.
Several flaws were found in the processing of some malformed HTML mail content. An HTML mail message containing such malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code as the user running Thunderbird. (CVE-2008-1233, CVE-2008-1235, CVE-2008-1236, CVE-2008-1237)
Several flaws were found in the display of malformed web content. An HTML mail message containing specially-crafted content could, potentially, trick a user into surrendering sensitive information. (CVE-2008-1234, CVE-2008-1238, CVE-2008-1241)
All Thunderbird users should upgrade to these updated packages, which contain backported patches to resolve these issues.