Multiple cross origin wrapper bypasses — Mozilla

Mozilla security researcher moz_bug_r_a4 reported a series of vulnerabilities in which objects that normally receive a XPCCrossOriginWrapper are constructed without the wrapper. This can lead to cases where JavaScript from one website may unsafely access properties of such an object which had been set by a different website. A malicious website could use this vulnerability to launch a XSS attack and run arbitrary JavaScript within the context of another site.