Paypal Bug Bounty #48 - Persistent Web Vulnerability

Document Title:
===============
Paypal Bug Bounty #48 - Persistent Web Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=830

PayPal Security UID:  dyf1f8cejz


Release Date:
=============
2013-03-28


Vulnerability Laboratory ID (VL-ID):
====================================
830


Common Vulnerability Scoring System:
====================================
3.5


Product & Service Introduction:
===============================
PayPal offers, both companies and individuals, a simple, quick and innovative solution of receiving money and making payments online. 

In ten years time, this company has become an authority in this market. Online buyers, eBay vendors, online stores and even the 
traditional offline companies. The number of users who trust PayPal with their transactions, continues to grow. 175 million PayPal 
accounts worldwide are certainly proof of that. PayPal uses a unique and extremely advanced system to prevent fraud, which guarantees 
a completely reliable and safe solution for real time payments online.

GP+ objectively analyzes and assesses the quality and  find ablility of online stores and, at the same time, examines the possibilities to avoid
attrition in the sales process. The base of this analysis is formed by: Google, Yahoo! and Microsoft Live, the W3C, Lipperhey in house research,
governments, renowned trade publications, worldwide specialists pool and research done by PayPal into the characteristics of the most successful
online stores worldwide.

(Copy of the Vendor Homepage:  https://www.paypal-gpplus.com/en/about/ )


Abstract Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered a input validation web vulnerability in the official PayPal GP+ Web Application Service.


Vulnerability Disclosure Timeline:
==================================
2013-01-02:     Researcher Notification & Coordination
2013-01-04:     Vendor Notification
2013-01-16:     Vendor Response/Feedback
2013-03-26:     Vendor Fix/Patch
2013-03-29:     Public Disclosure


Discovery Status:
=================
Published


Affected Product(s):
====================

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


Severity Level:
===============
Low


Technical Details & Description:
================================
A persistent input validation web vulnerability is detected in the official Paypal GP+ service application for anlayzing websites.
The vulnerability typus allows an attacker to inject own malicious script code in the vulnerable module on application-side (persistent).

The vulnerability is located in the `Indexability` section of the `Expert view` modules of the website, that has been analyzed.
The malicious code can be inserted in the `robots.txt` file of the website that will be analyzed. After the search is done, the 
malicious script code will be executed in the Robots.txt section in Home > Dashboard Analyses > Expert View > Indexability when 
processing to load the robots function exception-handling with the bound error listing. Exploitation of the vulnerability requires 
low user interaction without privileged web application user account.

Successful exploitation of the vulnerability result in persistent session hijacking, persistent phishing, persistent external redirects, 
persistent external malware loads via inject and persistent vulnerable module web context manipulation.

Vulnerable Section(s):
			[+] Paypal GP+ - (https://www.paypal-gpplus.com/en/dashboard/all/)

Vulnerable Module(s):

			[+] Expert View => Indexability

Vulnerable Parameter(s):
			[+] Robots.txt

Affected Module(s):
			[+] Expert View => Indexability - Exception Handling (Listing)


Proof of Concept (PoC):
=======================
The vulnerability can be exploited by remote attackers without user interaction and without privileged application user account. 
For demonstration or reproduce ...

A remote attacker can insert the malicious script code in the "robots.txt" of the website he would like to request. 
After the scan is done, the victim user goes to "Expert view" and choose Indexability, the malicious code will get executed in the Robots.txt section.

URL:  https://www.paypal-gpplus.com/en/dashboard/analysis/2728779/indexability/

Code Review: 
Indexability [Robots.txt]

<tr>
<td class="topic"><a class="expand" href="https://www.paypal-gpplus.com/en/dashboard/analysis/2728779/indexability/#">Robots.txt</a></td>
<td class="result">
Your <a href="http://xxx.0.61.xx/robots.txt" title="Open in a new window" target="_blank">robots.txt file</a> contains 
<strong>3</strong> disallows for user agents:
<ul><li><strong>[PERSISTENT INJECTED SCRIPT CODE!]</strong></li>
<li><strong>[PERSISTENT INJECTED SCRIPT CODE!]></strong></li><li><strong>[PERSISTENT INJECTED SCRIPT CODE!]></strong></li>
</ul></td></tr>



Solution - Fix & Patch:
=======================
2013-03-26:     Vendor Fix/Patch


Security Risk:
==============
The security risk of the persistent input validation vulnerabilities are estimated as medium(+).


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Ibrahim El-Sayed (the_storm) [[email protected]] [iel-sayed.blogspot.com]


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=========================
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