SeaMonkey is an open source web browser, email and newsgroup client, IRC chat client, and HTML editor. Several flaws were found in the processing of malformed web content. A web page containing malicious content could cause SeaMonkey to crash or, potentially, execute arbitrary code with the privileges of the user running SeaMonkey. A flaw was found in the way browser plug-ins interact. It was possible for a plug-in to reference the freed memory from a different plug-in, resulting in the execution of arbitrary code with the privileges of the user running SeaMonkey. An integer overflow flaw was found in the processing of malformed web content. A web page containing malicious content could cause SeaMonkey to crash or, potentially, execute arbitrary code with the privileges of the user running SeaMonkey. A flaw was found in the way SeaMonkey processed mail attachments. A specially-crafted mail message could cause SeaMonkey to crash. A flaw was found in the way SeaMonkey handled the "Content-Disposition: attachment" HTTP header when the "Content-Type: multipart" HTTP header was also present. A website that allows arbitrary uploads and relies on the "Content-Disposition: attachment" HTTP header to prevent content from being displayed inline, could be used by an attacker to serve malicious content to users. All SeaMonkey users should upgrade to these updated packages, which correct these issues. After installing the update, SeaMonkey must be restarted for the changes to take effect.