Red Hat Security Advisory 2015-1581-01 – Mozilla Firefox is an open source web browser. XULRunner provides the XUL Runtime environment for Mozilla Firefox. A flaw was discovered in Mozilla Firefox that could be used to violate the same-origin policy and inject web script into a non-privileged part of the built-in PDF file viewer. An attacker could create a malicious web page that, when viewed by a victim, could steal arbitrary files from the system running Firefox.