PayPal Unclaimed Payments Cross Site Scripting

`Document Title:  
===============  
Paypal Inc BB #14 - Persistent Payment Mail Vulnerability  
  
  
References (Source):  
====================  
http://www.vulnerability-lab.com/get_content.php?id=651  
  
  
Release Date:  
=============  
2013-11-20  
  
  
Vulnerability Laboratory ID (VL-ID):  
====================================  
651  
  
  
Common Vulnerability Scoring System:  
====================================  
5.2  
  
  
Product & Service 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.  
  
(Copy of the Homepage: www.paypal.com) [http://en.wikipedia.org/wiki/PayPal]  
  
  
Abstract Advisory Information:  
==============================  
The Vulnerability Laboratory Research Team discovered a Web Vulnerability in the official Paypal ecommerce website application.  
  
  
Vulnerability Disclosure Timeline:  
==================================  
2012-07-07: Researcher Notification & Coordination (Benjamin Kunz Mejri)  
2012-07-10: Vendor Notification (PayPal Site Security Team - Bug Bounty Program)  
2013-03-07: Vendor Response/Feedback (PayPal Site Security Team - Bug Bounty Program)  
2012-11-01: Vendor Fix/Patch (PayPal Inc Developer Team - Bug Bounty Reward $$$)  
2012-11-20: Public Disclosure (Vulnerability Laboratory)  
  
  
Discovery Status:  
=================  
Published  
  
  
Exploitation Technique:  
=======================  
Remote  
  
  
Severity Level:  
===============  
High  
  
  
Technical Details & Description:  
================================  
A persistent input validation vulnerability has been discovered in the official Paypal Inc website content management system & API.  
The bug allows remote attackers to inject own malicious script codes to the application-side of the paypal online-service.  
  
The vulnerability is located in the vulnerable `From` value of the Unclaimed Payments > Phone Payments (unconfirmed phone numbers) module.  
The script code execute occurs in the important `Phone Payments` request list of the verify a receiver via phonenumber function.   
The security risk of the persistent web vulnerabilities in the payments module is estimated as high with a cvss (common vulnerability   
scoring system) count of 5.1(+)|(-)5.2.  
  
The vulnerability can be exploited by remote attackers with low user inter action and low privileged paypal customer/pro/seller account.   
Successful exploitation of the vulnerability results in session hijacking (customers), account steal via persistent injects (listing),   
persistent phishing or persistent manipulation of module- or connected module context.  
  
  
Request Method(s):  
[+] POST  
  
Vulnerable Type(s):  
[+] Customer/Pro/Seller Accounts  
  
Vulnerable Section(s):  
[+] Unclaimed Payments  
  
Vulnerable Module(s):  
[+] Phone Payments  
  
Vulnerable Parameter(s):  
[+] From  
  
  
Proof of Concept (PoC):  
=======================  
The persistent input validation web vulnerability can be exploited by remote attackers with low privileged paypal customer/pro/seller account   
& low user inter action. For security demonstration or to reproduce the vulnerability follow the provided information below.  
  
  
PoC: Money Request Mail Notification  
  
<tbody><tr class="tableRowLightBlue"><td class="tableCellRegularSmall" colspan="2"><span class="emphasis">  
To</span></td><td> <span class="emphasis">From</span></td><td class="tableCellRegularSmall"><span class="emphasis">  
Amount</span> </td><td class="tableCellRegularSmall"> <span class="emphasis">Date Sent</span></td>  
<td class="tableCellRegularSmall"> <span class="emphasis">Status</span></td></tr><tr><td class="tableCellRegularSmall">  
<input name="phone_id" value="YbLGqPsRLZzdGAWnePuHErCuqMFSQXIxVdN33JaVMbXUnWvlp5_5H7Ju8R6LaZplCo7kApCTs3TNf0ol" type="radio">  
</td><td class="tableCellRegularSmall"> 408-678-0945</td><td class="tableCellRegularSmall"> Danh Nguyen's Test Store</td>  
<td class="tableCellRegularSmall">$1333337.00 USD </td><td class="tableCellRegularSmall"> Dec 3, 2010</td>  
<td class="tableCellRegularSmall"> Pending</td></tr><tr><td class="tableCellRegularSmall">  
<input name="phone_id" value="32vLCA4HtsQRr2cQEYpHcCf5wYT0V0kKrp4JnOSqkl78hb2qEUj3A8WvEssI1RqiRTyx3VM8chWSogB0" type="radio"></td>  
<td class="tableCellRegularSmall"> 408-983-5678</td>  
<td class="tableCellRegularSmall"> "><[PERSISTENT INJECTED SCRIPT CODE!]"> <</td><td   
class="tableCellRegularSmall">$50.00 USD </td><td   
  
  
POC URL1: https://www.paypal.com/us/cgi-bin/webscr?cmd=_unconfirmed-payments  
POC URL2: https://www.sandbox.paypal.com/us/cgi-bin/webscr?cmd=_unconfirmed-payments  
  
  
Solution - Fix & Patch:  
=======================  
The vulnerability can be patched by a secure encode and parse of the vulnerable From (phone_id) application value.  
  
Step 1: Encode and restrict the vulnerable input fields  
Step 2: Parse & filter the stored context when processing to reload as affected output  
  
  
Security Risk:  
==============  
The security risk of the persistent script code inject vulnerability is estimated as high(-).  
  
  
Credits & Authors:  
==================  
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected])  
  
  
Disclaimer & Information:  
=========================  
The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all warranties,   
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