XSS via plugins and unprotected Location object — Mozilla

Mozilla developer Blake Kaplan reported that the window.location object was made a normal overridable JavaScript object in the Firefox 3.6 browser engine (Gecko 1.9.2) because new mechanisms were developed to enforce the same-origin policy between windows and frames. This object is unfortunately also used by some plugins to determine the page origin used for access restrictions. A malicious page could override this object to fool a plugin into granting access to data on another site or the local file system. The behavior of older Firefox versions has been restored.