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PayPal Inc Bug Bounty #59 - Persistent Mail Encoding Vulnerability



Document Title:
===============
PayPal Inc Bug Bounty #59 - Persistent Mail Encoding Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=844

PayPal Security UID: CabdfGa


Release Date:
=============
2014-09-23


Vulnerability Laboratory ID (VL-ID):
====================================
844


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 Bill Later finance marketing service.


Vulnerability Disclosure Timeline:
==================================
2014-09-22:	Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
PayPal Inc
Product: BillMeLater - Finance & Marketing Service 2013 Q1


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


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


Technical Details & Description:
================================
A persistent mail encoding web vulnerability has been discovered in the official PayPal Inc Bill Later finance marketing service.
The vulnerability allows an attacker to inject own malicious script codes on the application-side of the affected service module.

The persistent input validation mail encoding web vulnerability is located in the `name` value of the vulnerable help submit form.
The attacker can send a POST method request with manipulated values through the help form application module to compromise the 
context of outgoign web-server mails. After the the request has been send an automatic reply arrives at the included inbox with 
the manipulated mail context of the successful help request ago. The script code execution occurs in the header section of the 
mail next to the introduction word `Hello [Name]`.

The security risk of the persistent web vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 3.5. 
Exploitation of the application-side vulnerability requires no privileged application user account and low or medium user interaction.
Successful exploitation of the vulnerability results in session hijacking, persistent phishing, persistent external redirect to malicious 
sources or persistent manipulation of affected or connected module context.

Request Method(s):
				[+] POST

Vulnerable Module(s):
				[+] PayPal Inc - BillMeLater (Apply)

Vulnerable Form(s):
				[+] ppfinportal > helpCenter > contact form

Vulnerable Parameter(s):
				[+] Name
				[+] Message

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


Proof of Concept (PoC):
=======================
The persistent vulnerability can be exploited by remote attackers with low privileged application user account and low required user interaction.
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.

--- PoC Session Logs [POST] ---
org.codehaus.groovy.grails.SYNCHRONIZER_TOKEN=e2a2492c-c330-43b2-80f1-65527e5f228e
org.codehaus.groovy.grails.SYNCHRONIZER_URI=
%2Fppfinportal%2FhelpCenter
name=Benjamin+Mejri+<>%20"><[PERSISTENT INJECTED SCRIPT CODE!]") <
email=admin%40vulnerability-lab.com
topic=GQ
message=ben+<>%20"><[PERSISTENT INJECTED SCRIPT CODE!]") <
contact_submit=Send+Message


Reference(s):
https://financing.paypal.com/ppfinportal/helpCenter#contact
https://financing.paypal.com/ppfinportal/helpCenter/messageSent


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure encode and parse of the name input values.
Restrict the input and disallow special chars and script code tags.
Filter the web-server mail notification with a proxy mechanism to prevent persistent script code executions in the header of outgoing service emails.


Security Risk:
==============
The security risk of the application-side mail encoding input validation web vulnerability is estimated as medium with a cvss of 3.5.


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


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