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Yahoo! Messenger 5.6 & Trillian (All Versions) - User Credential Disclosure Vulnerability
From: "Rafel Ivgi, The-Insider" <theinsider () 012 net il>
Date: Tue, 13 Apr 2004 01:24:19 +0200


Application:    Yahoo! Messenger 5.6 & Trillian (All Versions)
Vendors:         http://messenger.yahoo.com/
Platforms:        Windows
Bug:                 User Credential Disclosure Vulnerability
Risk:                 Medium
Exploitation:    Local - (or remote by sniffing)
Date:                1 Apr 2004
Author:             Rafel Ivgi, The-Insider
e-mail:              the_insider () mail com
web:                 http://theinsider.deep-ice.com


1) Introduction
2) Bugs
3) The Code


1) Introduction

Yahoo! Messenger one of the worlds most common, secure and easy to
use instant messangers.
You can stay connected to Yahoo! Messenger on your mobile phone
and message your mobile friends from your PC. More info Super Webcam
Enjoy high-quality, broadband video messaging with your friends! More info
New Emoticons Express yourself in whole new ways without writing a word!
See them all  IMVironments More IMVironments than ever before. (PC only)


2) Bug

While using Yahoo Messanger a user recieves mail to his yahoo inbox.
Yahoo Messanger as well as Trillian pop-up a message box that allows
the user to check his mail box.

Upon clicking this message box a temporary html file is dumped to windows
temp folder. This html file contains the username and the PASSWORD of the
users yahoo account, in PLAIN TEXT format.

In addition to that it sets up the "Remmeber me" option which saves the login cookie
which contains the login credentials - WITHOUT ASKING THE USER.

More over the connection opened uses standard HTTP protocol(which the username and password can be sniffed) instead of using the secure SSL login which is supported
by yahoo.


3) The Code

This is Proof Of Concept Code(the "temp" file which is generated):
------------------- CUT HERE -------------------

var username;


var password;


function submit () {








<body onLoad='submit();'>

<form method=post action="https://login.yahoo.com/config/login"; autocomplete=off name=login_form id=login_form onsubmit="return alert(document.forms['login_form'].login.value)">

<input type="hidden" name=".tries" value="1">
<input type="hidden" name=".src" value="ym">
<input type="hidden" name=".md5" value="">
<input type="hidden" name=".hash" value="">
<input type="hidden" name=".js" value="">
<input type="hidden" name=".last" value="2">
<input type="hidden" name="promo" value="">
<input type="hidden" name=".intl" value="us">
<input type="hidden" name=".bypass" value="">
<input type="hidden" name=".partner" value="">
<input type="hidden" name=".v" value="0">
<input type="hidden" name=".yplus" value="">
<input type="hidden" name=".emailCode" value="">
<input type="hidden" name="plg" value="">
<input type="hidden" name="stepid" value="">
<input type="hidden" name=".ev" value="">
<input type="hidden" name="hasMsgr" value="0">
<input type="hidden" name=".chkP" value="Y">
<input type="hidden" name=".done" value="http://mail.yahoo.com";>
<input type="hidden" id="login" name="login" size="17" value="">

<input type="hidden" name="passwd" id="passwd" size="17" maxlength="32">

<input type="hidden" name=".save" value="Sign In">
------------------- CUT HERE -------------------


--- Rafel Ivgi, The-Insider

"Only the one who sees the invisible , Can do the Impossible."
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html

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