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Skype Community - Mail Encoding Web Vulnerability #2
From: Vulnerability Lab <research () vulnerability-lab com>
Date: Mon, 26 Nov 2012 19:04:35 +0100

Title:
======
Skype Community - Mail Encoding Web Vulnerability #2


Date:
=====
2012-11-21


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=719


VL-ID:
=====
719


Common Vulnerability Scoring System:
====================================
4


Introduction:
=============
Skype is a proprietary voice-over-Internet Protocol service and software application originally created in 2003 by 
Swedish entrepreneur 
Niklas Zennström and his Danish partner Janus Friis. It has been owned by Microsoft since 2011. The service allows 
users to communicate 
with peers by voice, video, and instant messaging over the Internet. Phone calls may be placed to recipients on the 
traditional telephone 
networks. Calls to other users within the Skype service are free of charge, while calls to landline telephones and 
mobile phones are charged 
via a debit-based user account system. Skype has also become popular for its additional features, including file 
transfer, and videoconferencing. 
Competitors include SIP and H.323-based services, such as Linphone, as well as the Google Talk service, Mumble and 
Hall.com.

Skype has 663 million registered users as of September 2011. The network is operated by Microsoft, which has its Skype 
division headquarters 
in Luxembourg. Most of the development team and 44% of the overall employees of the division are situated in Tallinn 
and Tartu, Estonia.

Unlike most other VoIP services, Skype is a hybrid peer-to-peer and client–server system. It makes use of background 
processing on computers 
running Skype software. Skype`s original proposed name (Sky Peer-to-Peer) reflects this fact. Some network 
administrators have banned Skype 
on corporate, government, home, and education networks, citing reasons such as inappropriate usage of resources, 
excessive bandwidth usage, 
and security concerns.

(Copy of the Vendor Homepage: http://en.wikipedia.org/wiki/Skype)


Abstract:
=========
The Vulnerability Laboratory Research Team discovered a filter & mail encoding vulnerability in the official Skype 
Community Website Application.


Report-Timeline:
================
2012-10-08:     Researcher Notification & Coordination
2012-10-10:     Vendor Notification
2012-10-12:     Vendor Response/Feedback
2012-11-18:     Vendor Fix/Patch
2012-11-21:     Public or Non-Public Disclosure


Status:
========
Published


Affected Products:
==================
Microsoft
Product: Skype Community - Lithium Forums 2012 Q3


Exploitation-Technique:
=======================
Remote


Severity:
=========
High


Details:
========
A persistent input validation vulnerability is detected in the official Skype Community Website Application.
The vulnerability is located in the update post form with the unsanitized username in send mails.
Attackers can inject malicious persistent script code on application side of the skype skype community.
The vulnerability is located in the filter function of the username when skype community is processing 
to send a not parsed update mail. Remote attacker with low privileged application user accounts can change 
the username values to malicious persistent script code via POST. The result in a persistent script code 
inject via noreply () skype net  Successful exploitation of the vulnerability result in persistent phishing 
attacks, persistent session hijacking or mail context manipulation via persistent inject.

Vulnerable Section(s):
                        [+] Skype Community - (Forums)

Vulnerable Module(s):
                        [+] Notification Mail

Vulnerable Parameter(s):
                        [+] Username

Affected Section(s):
                        [+] Update Mail - Filter / Output Listing


Proof of Concept:
=================
The vulnerability can be exploited by remote attackers with low privileged application user account and with 
low or medium required user inter action. For demonstration or reproduce ...

<html>
<head>
<title>Skype Support Network Subscription: 1 Update: Betreff: Skype is Hacked ! Win32.Trojan.Agent.Gen 
schleicht sich durch die Accounts</title>
<link rel="important stylesheet" href="chrome://messagebody/skin/messageBody.css">
</head>
<body>
<table border=0 cellspacing=0 cellpadding=0 width="100%" class="header-part1"><tr><td><b>Betreff: 
</b>Skype Support Network Subscription: 1 Update: Betreff: Skype is Hacked ! Win32.Trojan.Agent.Gen schleicht sich 
durch die Accounts</td></tr><tr><td><b>Von: </b>Community Mailer <noreply () skype net></td></tr><tr><td><b>Datum: 
</b>06.10.2012 16:04</td></tr></table><table border=0 cellspacing=0 cellpadding=0 width="100%" class="header-part2"><tr>
<td><b>An: </b>rm01x <admin () vulnerability-lab com></td></tr></table><br>
<html>
        <head>
                <title>
                        Skype Support Network Subscription: 1  Update: Betreff: Skype is Hacked ! 
Win32.Trojan.Agent.Gen schleicht sich durch die Accounts                </title>
                <style type="text/css">
                        body, td { font: 10pt Arial, Helvetica; }
                </style>
        </head>
        <body class="lia-body email-template">
                <div class="lia-content subscription subscription-digest">
                        <div class="email-header">
                                <h2 class="email-greeting">
                                        Hello <[[PERSISTENT INJECTED SCRIPT CODE AS USERNAME!]]>,
                                </h2>
                                <p class="email-totals">
                                        You have 1  update for your Skype Support Network Subscriptions.
                                </p>
                                                        </div><!-- end email-header -->

                        <div class="email-main email-subscriptions">
                                                                        <hr />
                                        <div class="email-subscription">
<h3>Subscription to Thema: <a href="http://community.skype.com/t5/Skype-f%C3%BCr-Windows/Skype-is-Hacked-Win32-
Trojan-Agent-Gen-schleicht-sich-durch-die/td-p/1086370">Skype is Hacked ! Win32.Trojan.Agent.Gen schleicht sich 
durch die Accounts</a> (1 Update)</h3>
<div class="email-subscription-notifications">
<div class="email-subscription-notification">

There was a new Antworten.<br>

<table class="notification-metadata" border=0 cellspacing=0 cellpadding=2>
<tr><td>Subject:  </td><td> <a href="http://community.skype.com/t5/Skype-f%C3%BCr-Windows/Skype-is-Hacked-Win32-
Trojan-Agent-Gen-schleicht-sich-durch-die/m-p/1101468#M6531">Betreff: Skype is Hacked ! Win32.Trojan.Agent.Gen 
schleicht 
sich durch die Accounts</a></td></tr>
<tr><td>Author:</td><td>Methu (New Member)</td></tr>
<tr><td>Date:</td><td>06-10-2012 16:04</td></tr>
</table>
                                                                
<p class="email-notification-body-separate">
<a href="http://community.skype.com/t5/Skype-f%C3%BCr-Windows/Skype-is-Hacked-Win32-Trojan-Agent-Gen-
schleicht-sich-durch-die/m-p/1101468#M6531">View</a>
</p>
</div><!-- end email-subscription-notification -->
</div><!-- end email-subscription-notifications -->
</div><!-- end email-subscription -->
</div><!-- end email-subscriptions -->
                        <hr />
                        <div class="email-footer">
                                <p class="manage-normal">
                                        To manage your subscriptions or to change your subscription options,
                                        click <a href="http://community.skype.com/skypec/user_subscriptions";>here</a>.
                                </p>
                                <p class="manage-alternate">
                                        If this link doesn't work: 
                                        <ol>
                                                <li>Log on to Skype Support Network.</li>
                                                <li>Click <b>My Profile</b>.</li>
                                                <li>Click the <b>Subscriptions & Bookmarks</b> tab. </li>
                                                <li>Change your settings and click <b>Save Changes</b>. </li>
                                        </ol>
                                </p>
                                <p class="manage-thanks">Thanks for being a Skype Support Network member.</p>
                                <p class="manage-team">
                                        <i>Your Skype Support Network Team</i>
                                </p>
                                <font size=-1>
                                        <p class="manage-sent-to">
                                                Skype Support Network sent this message to admin () vulnerability-lab 
com 
                                        </p>
<p class="manage-unsubscribe">
Did not request this email yourself? Click <a href="http://community.skype.com/t5/user/RemoveUserEmailPage/user-id
/1915382/mail-message-tracking/H7YSNPPZVRU0CL">this link</a> to permanently prevent your email address being used on 
our community (NB: You won't be able to use the address yourself in the future).
        
                        </p>
                                </font>
                        </div><!-- end email-subscriptions-manage -->
                </div><!-- end lithium-content -->
        </body>
</html>
</body>
</html>


Solution:
=========
The vulnerability can be patched by parsing the context with the lithium api request of the community application 
formular.


Risk:
=====
The security risk of the filter & mail encoding vulnerability is estimated as medium(+)|(-)high.


Credits:
========
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm () vulnerability-lab com)


Disclaimer:
===========
The information provided in this advisory is provided as it is without any warranty. Vulnerability-Lab disclaims all 
warranties, 
either expressed or implied, including the warranties of merchantability and capability for a particular purpose. 
Vulnerability-
Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss 
of business 
profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such 
damages. Some 
states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing 
limitation 
may not apply. We do not approve or encourage anybody to break any vendor licenses, policies, deface websites, hack 
into databases 
or trade with fraud/stolen material.

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                                        Copyright © 2012 | Vulnerability Laboratory



-- 
VULNERABILITY RESEARCH LABORATORY
LABORATORY RESEARCH TEAM
CONTACT: research () vulnerability-lab com


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