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Firefox / IE6 crash on javascript nested loops
Firefox / IE6 crash on javascript nested loops
Firefox / IE6 crash on javascript nested loops

ground418 security advisory

Date: 30-10-2007
Subject: Firefox / IE6 crash on javascript nested loops
Author: Vincent Audet Menard
Original file: http://www.ground418.org/exploits/read.php?file=07-ffox-loops 
Risk: low

Tested on: IE6, IE7, Firefox, Safari
Vulnerable: IE6 and older, Firefox and older (mac, window, linux)
Not Vulnerable: IE7, Safari 2.0.4

-[ Remote Firefox / IE6 crash ]

It's possible to crash and/or force the user to kill Firefox
and IE6 by coding an endless loop using javascript functions onblur()
and onfocusout(). By using 2 text input fields that are respectively
setting focus on each other, you can force the user to quit the
browser and eventually crash it if the user holds the enter key when a
javascript alert window appears.

This bug seems to be fixed in Internet Explorer 7, Microsoft seems to
have added a counter that limits the number of consecutive pop-up
A variation of that bug has been reported to firefox a few years ago
(see related file), but seems to never have been posted on official
security channels.

-[ Related files ]

Original file:

Proof of concept available on (at your own risk):

Related on bugzilla

Vincent A. M=E9nard
CTO - Heptacube inc.

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