There had been a report of vulnerability of Mozilla Firefox to a bug (Via Pradeep)....though it seems that , it got fixed in a day, I couldn't know(simply because I don't know the technicalities of the problem) the real extent of the severity of the bug....the attack is one that of spoofing....it seems that the issue might be because of the "Modernity" of the browser.....the modern browsers are IDN enabled...while IE isn't. This support lets the attackers to scoop the Domain name URL's....the stuff is like this....the same URL might lead to different sites....this is because of a small tweak with the Unicode characters....this sort of attack is called Homograph Attacks . All the major browsers are vulnerable except the IE...the immediate and short term response of the Mozilla team has been to disable the IDN facility in the browser...but it doesn't seem to be a viable long term solution.....
Though there are reports that there is a fix to this vulnerability, it remains to be included in the newer versions of Firefox....Read the official response of the Mozilla....