Updated firefox packages that fix several security issues and one bug are now available for Red Hat Enterprise Linux 4, 5, and 6. The Red Hat Security Response Team has rated this update as having critical security impact. Common Vulnerability Scoring System base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section. Description Mozilla Firefox is an open source web browser. XULRunner provides the XUL Runtime environment for Mozilla Firefox. A flaw was found in the way Firefox sanitized HTML content in extensions. If an extension loaded or rendered malicious content using the ParanoidFragmentSink class, it could fail to safely display the content, causing Firefox to execute arbitrary JavaScript with the privileges of the user running Firefox. A flaw was found in the way Firefox handled dialog boxes. An attacker could use this flaw to create a malicious web page that would present a blank dialog box that has non-functioning buttons. If a user closes the dialog box window, it could unexpectedly grant the malicious web page elevated privileges. 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. Several flaws were found in the way Firefox handled malformed JavaScript. A website containing malicious JavaScript could cause Firefox to execute that JavaScript with the privileges of the user running Firefox. A flaw was found in the way Firefox handled malformed JPEG images. A website containing a malicious JPEG image could cause Firefox to crash or, potentially, execute arbitrary code with the privileges of the user running Firefox. A flaw was found in the way Firefox handled plug-ins that perform HTTP requests. If a plug-in performed an HTTP request, and the server sent a 307 redirect response, the plug-in was not notified, and the HTTP request was forwarded. The forwarded request could contain custom headers, which could result in a Cross Site Request Forgery attack. For technical details regarding these flaws, refer to the Mozilla security advisories for Firefox 3.6.14. You can find a link to the Mozilla advisories in the References section of this erratum. This update also fixes the following bug: On Red Hat Enterprise Linux 4 and 5, running the "firefox setDefaultBrowser" command caused warnings such as the following: libgnomevfs-WARNING **: Deprecated function. User modifications to the MIME database are no longer supported. This update disables the "setDefaultBrowser" option. Red Hat Enterprise Linux 4 users wishing to set a default web browser can use Applications -