The latest vulnerability of Microsoft’s Internet Explorer lets a hacker display any website, while the address bar shows a trusted website.
Obviously, this could generate scams such as displaying a fake website of your financial institutions to get your password. All the attackers would have to do is to mimic the appearance of the real website homepage, and display a maintenance message after you typed in your login information. Most people would not realize what just happened.
No attack of this type has been reported yet, but this could potentially happen.