Paypal Bug Bounty #11 - Redirection Web Vulnerability

[Vulnerability Lab <research () vulnerability-lab com>]

Title:
======
Paypal Bug Bounty #11 - Redirection Web Vulnerability


Date:
=====
2012-11-22


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=648


VL-ID:
=====
648


Common Vulnerability Scoring System:
====================================
2


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 Web Vulnerability in the official Paypal ecommerce website 
application.



Report-Timeline:
================
2012-07-06:     Researcher Notification & Coordination
2012-07-06:     Vendor Notification
2012-08-10:     Vendor Response/Feedback
2012-10-29:     Vendor Fix/Patch
2012-11-22:     Public or Non-Public Disclosure


Status:
========
Published


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


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


Details:
========
A client side redirection vulnerability is detected in the official Paypal ecommerce website content management system 
(Customer/Pro/Seller).
The bugs allow remote attackers to form client side requests to redirect a victim with the report (bericht) function 
from paypal to an external 
malicious target (website|server).  The vulnerability is located in the Reports (Berichte) - Export module with the 
bound vulnerable back-to-portal 
& portal_url parameter. The vulnerability can be exploited by remote attackers with medium or high required user inter 
action and without privileged 
Customer/Pro/Seller account. Successful exploitation of the vulnerability can lead exter redirections, client side spam 
mails & client side phishing mails.

Vulnerable Type(s):
                          [+] Customer/Pro/Seller Accounts


Vulnerable Section(s):
                          [+] Reports (Berichte) - Export


Vulnerable Module(s):
                          [+] Export as File (Send Mail)


Vulnerable Parameter(s):
                          [+] back-to-portal&portal_url


Proof of Concept:
=================
The redirect vulnerability can be exploited by remote attackers without Customer/Pro/Seller account & with medium or 
high required 
user inter action. For demonstration or reproduce ...

Original:
https://www.paypal.com/de/cgi-bin/?cmd=_back-to-portal&portal_url=https://business.paypal.com/mfportal/PortalApp/DisplayReport?
id=6Mg3Wa-9QkuNW-QKrNy3sl0rKZYPB19GysMYz0VcZxY

PoC:
https://www.paypal.com/de/cgi-bin/?cmd=_back-to-portal&portal_url=https://vulnerability-lab.com
https://www.paypal.com/de/cgi-bin/?cmd=_back-to-portal&portal_url=https://vulnerability-lab.com/malicious-test.html


Solution:
=========
Restrict the url request for external targets by implementing a whitelist for trusted/allowed websites or portals.
Form a secure exception-handling around to disallow unauthorized external target websites or portals.

2012-10-29:     Vendor Fix/Patch


Risk:
=====
The security risk of the redirection vulnerability is estimated as low(+).


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 
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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



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