User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.81 Safari/537.36
Steps to reproduce:
1. created a few iframes
2. attached each of them onbeforeunload event
3. waited for user to exit the page
Users are trapped in the web page.
There should be a limit of onbeforeunload event callback for outer window or the browser should prevent onbeforeunload event to attach an iframe's window.
Thanks for the report.
*** This bug has been marked as a duplicate of bug 636374 ***