Mozilla Thunderbird is a standalone mail and newsgroup client.
Several flaws were found in the processing of malformed HTML content. An HTML mail containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code as the user running Thunderbird. (CVE-2008-2785, CVE-2008-2798, CVE-2008-2799, CVE-2008-2811)
Several flaws were found in the way malformed HTML content was displayed. An HTML mail containing specially-crafted content could, potentially, trick a Thunderbird user into surrendering sensitive information. (CVE-2008-2800)
Two local file disclosure flaws were found in Thunderbird. An HTML mail containing malicious content could cause Thunderbird to reveal the contents of a local file to a remote attacker. (CVE-2008-2805, CVE-2008-2810)
A flaw was found in the way a malformed .properties file was processed by Thunderbird. A malicious extension could read uninitialized memory, possibly leaking sensitive data to the extension. (CVE-2008-2807)
A flaw was found in the way Thunderbird displayed information about self-signed certificates. It was possible for a self-signed certificate to contain multiple alternate name entries, which were not all displayed to the user, allowing them to mistakenly extend trust to an unknown site. (CVE-2008-2809)
All Thunderbird users should upgrade to these updated packages, which contain backported patches to resolve these issues.