(RHSA-2011:1438) Moderate: thunderbird security update

Mozilla Thunderbird is a standalone mail and newsgroup client.

A cross-site scripting (XSS) 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. (CVE-2011-3648)

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.