http://www.azarask.in/blog/post/a-new-t ... ng-attack/
After you read how it works you can click on another tab, watch as the tab will turn to Gmail icon and description and when you go back it will "gmail login" page. It's just an image to provide an example.
How The Attack Works
1. A user navigates to your normal looking site.
2. You detect when the page has lost its focus and hasn’t been interacted with for a while.
4. As the user scans their many open tabs, the favicon and title act as a strong visual cue—memory is malleable and moldable and the user will most likely simply think they left a Gmail tab open. When they click back to the fake Gmail tab, they’ll see the standard Gmail login page, assume they’ve been logged out, and provide their credentials to log in. The attack preys on the perceived immutability of tabs.
5. After the user has entered their login information and you’ve sent it back to your server, you redirect them to Gmail. Because they were never logged out in the first place, it will appear as if the login was successful.