PayPal Cross Site Scripting

`Title:  
======  
Paypal Bug Bounty #10 - Persistent Web Vulnerability  
  
  
Date:  
=====  
2013-01-24  
  
  
References:  
===========  
http://www.vulnerability-lab.com/get_content.php?id=647  
  
PayPal UID: ixb165sfi  
  
  
VL-ID:  
=====  
647  
  
  
Common Vulnerability Scoring System:  
====================================  
3.5  
  
  
Introduction:  
=============  
PayPal is a global e-commerce business allowing payments and money transfers to be made through the Internet. Online money   
transfers serve as electronic alternatives to paying with traditional paper methods, such as checks and money orders. Originally,   
a PayPal account could be funded with an electronic debit from a bank account or by a credit card at the payer s choice. But some   
time in 2010 or early 2011, PayPal began to require a verified bank account after the account holder exceeded a predetermined   
spending limit. After that point, PayPal will attempt to take funds for a purchase from funding sources according to a specified   
funding hierarchy. If you set one of the funding sources as Primary, it will default to that, within that level of the hierarchy   
(for example, if your credit card ending in 4567 is set as the Primary over 1234, it will still attempt to pay money out of your   
PayPal balance, before it attempts to charge your credit card). The funding hierarchy is a balance in the PayPal account; a   
PayPal credit account, PayPal Extras, PayPal SmartConnect, PayPal Extras Master Card or Bill Me Later (if selected as primary   
funding source) (It can bypass the Balance); a verified bank account; other funding sources, such as non-PayPal credit cards.  
The recipient of a PayPal transfer can either request a check from PayPal, establish their own PayPal deposit account or request   
a transfer to their bank account.  
  
PayPal is an acquirer, performing payment processing for online vendors, auction sites, and other commercial users, for which it   
charges a fee. It may also charge a fee for receiving money, proportional to the amount received. The fees depend on the currency   
used, the payment option used, the country of the sender, the country of the recipient, the amount sent and the recipient s account   
type. In addition, eBay purchases made by credit card through PayPal may incur extra fees if the buyer and seller use different currencies.  
  
On October 3, 2002, PayPal became a wholly owned subsidiary of eBay. Its corporate headquarters are in San Jose, California, United   
States at eBay s North First Street satellite office campus. The company also has significant operations in Omaha, Nebraska, Scottsdale,   
Arizona, and Austin, Texas, in the United States, Chennai, Dublin, Kleinmachnow (near Berlin) and Tel Aviv. As of July 2007, across   
Europe, PayPal also operates as a Luxembourg-based bank.  
  
On March 17, 2010, PayPal entered into an agreement with China UnionPay (CUP), China s bankcard association, to allow Chinese consumers   
to use PayPal to shop online.PayPal is planning to expand its workforce in Asia to 2,000 by the end of the year 2010.  
Between December 4ñ9, 2010, PayPal services were attacked in a series of denial-of-service attacks organized by Anonymous in retaliation   
for PayPal s decision to freeze the account of WikiLeaks citing terms of use violations over the publication of leaked US diplomatic cables.  
  
(Copy of the Homepage: www.paypal.com) [http://en.wikipedia.org/wiki/PayPal]  
  
  
Abstract:  
=========  
The Vulnerability Laboratory Research Team discovered a persistent Web Vulnerability in the official Paypal ecommerce website application.  
  
  
Report-Timeline:  
================  
2012-07-06: Researcher Notification & Coordination  
2012-07-06: Vendor Notification  
2012-07-11: Vendor Response/Feedback  
2013-12-10: Vendor Fix/Patch  
2012-01-24: Public Disclosure  
  
  
Status:  
========  
Published  
  
  
Affected Products:  
==================  
PayPal Inc  
Product: PayPal Account Service Application 2012 Q4  
  
  
Exploitation-Technique:  
=======================  
Remote  
  
  
Severity:  
=========  
Medium  
  
  
Details:  
========  
A persistent input validation vulnerability is detected in the official Paypal ecommerce website content management system (Customer/Pro/Seller).  
The bugs allow remote attackers to implement/inject malicious script code on the application side (persistent) of the paypal web service.  
  
The vulnerability is located in the Geld buchen > Transcaction > Abbuchung prüfen module with the bound vulnerable bankname parameter.   
The bug affects the important Abbuchung prüfen listing of the paypal core application. The remote attacker can inject own the malicious   
script codes by requesting the transaction check page with a manipulated bankname parameter.   
  
The vulnerability can be exploited by remote attackers with low required user inter action and privileged Customer/Pro/Seller account.  
Successful exploitation of the vulnerability can lead to session hijacking (customers), account steal via persistent web attack, persistent   
phishing or stable (persistent) web context manipulation of the vulnerable module.  
  
Vulnerable Type(s):  
[+] Customer/Pro/Seller Accounts  
  
Vulnerable Section(s):  
[+] Geld buchen > Transcaction > Abbuchung prüfen > Bankname  
  
Vulnerable Module(s):  
[+] Name der Bank (Name of Bank & Companyname)  
  
Vulnerable Parameter(s):  
[+] bankname  
  
Affected Section(s):  
[+] Abbuchung prüfen (Listing)  
  
  
Proof of Concept:  
=================  
The vulnerability can be exploited by remote attackers with Customer/Pro/Seller Account & low required user inter action.  
For demonstration or reproduce ...  
  
Review: Geld buchen > Transcaction > Abbuchung prüfen (Listing)  
  
<tbody><tr><th>Betrag</th><td>¤0,80 EUR</td></tr><tr><th>Name des Kontoinhabers</th><td>Evolution Security</td></tr>  
<tr><th>Name der Bank</th><td><[PERSISTENT INJECTED SCRIPT CODE!]"></td></tr><tr><th>Bankleitzahl</th><td>  
51050352</td></tr><tr><th>Kontonummer</th><td>x-13371</td></tr>  
</tbody></table></div>  
  
URL Session:  
https://www.paypal.com/de/cgi-bin/webscr?cmd=_flow&  
SESSION=wbOxy2QWgxYBr5jKfOfH6E49y4duJ5yOQfN2yKqZgD-622kOCZZihkCZi7O&  
dispatch=5885d80a66c0db1f8e263113d3faee8d2394db9703d295b4a2116480ee01a05c  
  
  
Solution:  
=========  
Restrict the bankname input fields and parse with an exception handling or secure filter mask.   
Parse the bankname details output listing in Abbuchung prüfen (Listing) to prevent script code injects/executions.  
  
  
Risk:  
=====  
The security risk of the persistent script code inject vulnerability is estimated as medium(+).  
  
  
Credits:  
========  
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected])  
  
  
Disclaimer:  
===========  
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