Mozilla Thunderbird is a standalone mail and newsgroup client. A cross-site scripting flaw was found in the way Thunderbird handled certain multibyte character sets. Malicious, remote content could cause Thunderbird to run JavaScript code with the permissions of different remote content. Note: This issue cannot be exploited by a specially-crafted HTML mail message as JavaScript is disabled by default for mail messages. It could be exploited another way in Thunderbird, for example, when viewing the full remote content of an RSS feed. All Thunderbird users should upgrade to this updated package, which resolves this issue. All running instances of Thunderbird must be restarted for the update to take effect.