Mozilla Firefox is an open source web browser. XULRunner provides the XUL Runtime environment for Mozilla Firefox. Several flaws were found in the processing of malformed web content. A web page containing malicious content could cause Firefox to crash or, potentially, execute arbitrary code with the privileges of the user running Firefox. 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, and Looben Yang as the original reporters of these issues. All Firefox users should upgrade to these updated packages, which contain Firefox version 38.3.0 ESR, which corrects these issues. After installing the update, Firefox must be restarted for the changes to take effect.