Mozilla Thunderbird is a standalone mail and newsgroup client. Several flaws were found in the processing of malformed HTML mail content. An HTML mail message containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code as the user running Thunderbird. Several flaws were found in the way malformed content was processed. An HTML mail message containing specially-crafted content could potentially trick a Thunderbird user into surrendering sensitive information. Note: JavaScript support is disabled by default in Thunderbird. None of the above issues are exploitable unless JavaScript is enabled. All Thunderbird users should upgrade to this updated package, which resolves these issues. All running instances of Thunderbird must be restarted for the update to take effect.