An updated thunderbird package that fixes one security issue is now available for Red Hat Enterprise Linux 5 and 6. The Red Hat Security Response Team has rated this update as having critical security impact. A Common Vulnerability Scoring System base score, which gives a detailed severity rating, is available from the CVE link in the References section. Description Mozilla Thunderbird is a standalone mail and newsgroup client. A flaw was found in the way Thunderbird handled security wrappers. Malicious content could cause Thunderbird to execute arbitrary code with the privileges of the user running Thunderbird. Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges moz_bug_r_a4 as the original reporter. 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 corrects this issue. After installing the update, Thunderbird must be restarted for the changes to take effect.