Updated xulrunner packages that fix one security issue are 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 XULRunner provides the XUL Runtime environment for applications using the Gecko layout engine. A heap-based buffer overflow flaw was found in the way XULRunner handled PNG images. A web page containing a malicious PNG image could cause an application linked against XULRunner to crash or, potentially, execute arbitrary code with the privileges of the user running the application. All XULRunner users should upgrade to these updated packages, which correct this issue. After installing the update, applications using XULRunner must be restarted for the changes to take effect.