Check out this Firefox-only exploit (Score 2, Informative)

The Schmoo Group (http://www.shmoo.com/) 0wned Firefox and basically everything except IE with International Domain Support. It might be a wise security move to turn this functionality off in your browsers until updated versions address the vulnerability, as phishing scams are expected to erupt utilizing this exploit shortly.

Details here: http://www.shmoo.com/idn/homograph.txt

Watch the exploit in action here: http://www.shmoo.com/idn/

To patch this (in most browsers):

1) Goto your Firefox address bar. Enter about:config and press enter. Firefox will load the (large!) config page.
2) Scroll down to the line beginning network.enableIDN -- this is International Domain Name support, and it is causing the problem here. We want to turn this off -- for now. Ideally we want to support international domain names, but not with this problem.
3) Double-click the network.enableIDN label, and Firefox will show a dialog set to 'true'. Change it to 'false' (no quotes!), click Ok. You are done.
4) Go check out the shmoo demo (above) again and notice it no longer works.