Mozilla Thunderbird is a standalone mail and newsgroup client. Several flaws were found in the processing of malformed HTML content. An HTML mail message containing malicious content could possibly lead to arbitrary code execution with the privileges of the user running Thunderbird. An arbitrary memory write flaw was found in the way Thunderbird handled out-of-memory conditions. If all memory was consumed when a user viewed a malicious HTML mail message, it could possibly lead to arbitrary code execution with the privileges of the user running Thunderbird. An integer overflow flaw was found in the way Thunderbird handled the HTML frameset tag. An HTML mail message with a frameset tag containing large values for the "rows" and "cols" attributes could trigger this flaw, possibly leading to arbitrary code execution with the privileges of the user running Thunderbird. A flaw was found in the way Thunderbird handled the HTML iframe tag. An HTML mail message with an iframe tag containing a specially-crafted source address could trigger this flaw, possibly leading to arbitrary code execution with the privileges of the user running Thunderbird. A flaw was found in the way Thunderbird displayed multiple marquee elements. A malformed HTML mail message could cause Thunderbird to execute arbitrary code with the privileges of the user running Thunderbird. A flaw was found in the way Thunderbird handled the nsTreeSelection element. Malformed content could cause Thunderbird to execute arbitrary code with the privileges of the user running Thunderbird. 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.