Mozilla Thunderbird is a standalone mail and newsgroup client. Several flaws were found in the processing of malformed web content. A web page containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird. Two information leak flaws were found in the processing of malformed web content. A web page containing malicious content could cause Thunderbird to disclose sensitive information or, in certain cases, crash. Note: All of the above issues cannot be exploited by a specially crafted HTML mail message because JavaScript is disabled by default for mail messages. However, they could be exploited in other ways in Thunderbird . Red Hat would like to thank the Mozilla project for reporting these issues. Upstream acknowledges Andrew Osmond, Olli Pettay, Andrew Sutherland, Christian Holler, David Major, Andrew McCreight, Cameron McCormack, Ronald Crane, Mario Gomes, and Ehsan Akhgari as the original reporters of these issues. For technical details regarding these flaws, refer to the Mozilla security advisories for Thunderbird 38.3.0 You can find a link to the Mozilla advisories in the References section of this erratum. All Thunderbird users should upgrade to this updated package, which contains Thunderbird version 38.3.0, which corrects these issues. After installing the update, Thunderbird must be restarted for the changes to take effect.