Mozilla Thunderbird is a standalone mail and newsgroup client. A race condition flaw was found in the way Thunderbird handled Document Object Model element properties. An HTML mail message containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird. 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 with the privileges of the user running Thunderbird. A same-origin policy bypass flaw was found in Thunderbird. Remote HTML content could steal private data from different remote HTML content Thunderbird had loaded. Note: JavaScript support is disabled by default in Thunderbird. The above issues are not exploitable unless JavaScript is enabled. A flaw was found in the script that launches Thunderbird. The LD_LIBRARY_PATH variable was appending a "." character, which could allow a local attacker to execute arbitrary code with the privileges of a different user running Thunderbird, if that user ran Thunderbird from within an attacker-controlled directory. 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.