Mozilla engineers concluded early on in the process that the problem was a fairly minor one that was unlikely to cause the vast majority of users any confusion or be exploited by attackers. The bug, which is related to the way that Firefox renders URLs in iFrames, was submitted to Mozilla s Bugzilla bug-tracking system on June 7. Because the bug doesn t pose much risk to users, Mozilla has no plans to issue a fix for it at this point. Mozilla will be adding content security policy into the browser itself.
Source: https://threatpost.com/mozilla-bug-seen-very-low-risk-081810/74349/