Document Title:
===============
PayPal Inc Bug Bounty #61 - Persistent Mail Encoding Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=846

PayPal Security UID: bzbe1he


Release Date:
=============
2013-10-16


Vulnerability Laboratory ID (VL-ID):
====================================
846


Common Vulnerability Scoring System:
====================================
3.5


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 Vendor Homepage: www.paypal.com) [http://en.wikipedia.org/wiki/PayPal]


Abstract Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered in the official PayPal Inc (Ebay) MainStreet finance service company website.


Vulnerability Disclosure Timeline:
==================================
2013-01-28:  Researcher Notification & Coordination (Benjamin Kunz Mejri)
2013-01-31:  Vendor Notification (PayPal Site Security Team - Bug Bounty Program)
2013-10-12:  Vendor Response/Feedback (PayPal Site Security Team - Bug Bounty Program)
2013-10-15:  Vendor Fix/Patch (PayPal Developer Team)
2013-10-16:  Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
PayPal Inc
Product: MainStreet - Ebay Paypal Marketing Service 2013 Q1


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


Severity Level:
===============
Medium


Technical Details & Description:
================================
A persistent mail encoding web vulnerability is detected in the official PayPal Inc (Ebay) MainStreet Finance Service Web Application.
The vulnerability allows to send via POST method malicious mails to customers with own injected persistent script code.

The persistent input validation mail encoding vulnerability is located in the paypal mainstreet service application. Remote attackers 
can inject malicious script codes via POST method request in the profile name value. The remote attacker can send the manipulated 
request with the `Send to Friends` function to exploit paypal customer accounts. The script code executes in the mail response of the 
feedback and send to friends function.

Exploitation of the vulnerability requires no privileged application user account and low or medium user interaction.
Successful exploitation of the vulnerability results in persistent phishing , persistent session hijacking and persistent 
mail context manipulation.

Vulnerable Service(s):
        [+] PayPal Inc - MainStreet (also Ebay)

Vulnerable Module(s):
        [+] Send to Friends

Vulnerable Parameter(s):
        [+] Name (Sender: Friend)

Affected Module(s):
        [+] Notification Mail (Web Server) [DL-BML-MerchantPortalFeedback@ebay.com]


Proof of Concept (PoC):
=======================
The vulnerability can be exploited by remote attackers with low privileged application user account and low or medium required user interaction.
For demonstration or reproduce ...

Review: x has forwarded a page to you from eBay Inc. PayPal Main Street

    <thead>
        <tr>
          <td>
            <h1 style="font-family:Arial,Helvetica,sans-serif; font-size:18px;">
<a href="http://www.ebaymainstreet.com/forward/emailref?path=%3Cfront%3E" title="eBay Inc. Main Street"><img src="http://www.ebaymainstreet.com/sites/default/files/ebay_mainstreet_logo.png" alt=""> eBay Inc. Main Street</a></h1>
          </td>
        </tr>
      </thead>
      <tbody>
        <tr>
          <td style="font-family:Arial,Helvetica,sans-serif; font-size:12px;">
            <a href="mailto:01x445@gmail.com">>"<>;%20%20%20%20>
"<[PERSISTENT INJECTED SCRIPT CODE!])<" <="" a=""> thought you would like to see this page from the eBay Inc. Main Street web site.
<p>Message from Sender</p><p><my message :O)<</p>


Reference(s):
http://www.paypalmainstreet.com/ [FORWARD]
http://www.ebaymainstreet.com/

http://www.ebaymainstreet.com/forward?path=node/94374 (Insert)
http://www.paypalmainstreet.com/forward?path=node/94374 (Insert)


Security Risk:
==============
The security risk of the persistent mail encoding input validation web vulnerability is estimated as medium(+).


Credits & Authors:
==================
Vulnerability Laboratory [Research Team]  -    Benjamin Kunz Mejri (bkm@vulnerability-lab.com)


Disclaimer & Information:
=========================
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