Document Title:
===============
PayPal Inc Bug Bounty #119 - URL Redirect Web Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1610


Release Date:
=============
2015-10-01


Vulnerability Laboratory ID (VL-ID):
====================================
1610


Common Vulnerability Scoring System:
====================================
2.4


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:
==============================
An independent vulnerability laboratory researcher discovered a client-side url redirect web vulnerability in the official PayPal Inc Notify online service web-application.


Vulnerability Disclosure Timeline:
==================================
2015-08-28: Researcher Notification & Coordination (Rui Silva)
2015-08-09: Vendor Notification (PayPal Security Team - Bug Bounty Program)
2015-09-08: Vendor Response/Feedback (PayPal Security Team - Bug Bounty Program)
2015-09-24: Vendor Fix/Patch (PayPal Inc Developer Team)
2015-10-01: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
PayPal Inc
Product: PayPal - Online Service Web Application 2015 Q3


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


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


Technical Details & Description:
================================
A low severity and client-side url redirect web vulnerability has been discovered in the official PayPal Inc Notify online service web-application.
The vulnerability allows remote attackers to form malicious links as client-side GET method requests to manipulate a return url.

The vulnerability is located in the redirectUrl value of the main_home module. Remote attackers are able to prepare manipulated client-side application 
to browser requests. Thus results in a client-side context manipulation after the redirect itself. After some seconds the service refreshs and allows 
to load the url by a special crafted payload that bypass the validation procedure.

The vulnerability can be exploited by remote attackers without privilege web-application user accounts and with low required user interaction.
Successful exploitation results in client side phishing and client-side external redirect to malicious sources.

Request Method(s):
            [+] GET

Vulnerable Module(s):
                                                [+] PayPal (Notify)

Vulnerable Parameter(s):
                                                [+] redirectUrl

Affected Module(s):
                                                [+] paypal-notify.com/main_home


Proof of Concept (PoC):
=======================
The open redirect web vulnerability can be exploited by remote attackers without privilege web-application user account and low user interaction.
For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue.

Manual steps to reproduce the vulnerability ...
1. First go to: paypal-notify.com/main_home?redirectUrl=
2. Now you have to add after  redirectUrl= parameter this: //google.pt
3. Edited URL will be like this: paypal-notify.com/main_home?redirectUrl=//google.pt
4. You can add any site after //
5. Now open Edited Url on a new tab on broswer
6. Now choose option Login with Paypal 
7. Wait 6/7 seconds and you will be redirected to google.pt


Solution - Fix & Patch:
=======================
2015-09-10: Vendor Fix/Patch (PayPal Inc Developer Team)


Security Risk:
==============
The security risk of the client-side url redirect web vulnerability in the paypal notifyme service is estimated as low. (CVSS 2.4)


Credits & Authors:
==================
Rui Silva (http://www.vulnerability-lab.com/show.php?user=Rui%20Silva)


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