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Paypal Inc Bug Bounty #104 - Persistent Exception Vulnerability
From: Vulnerability Lab <research () vulnerability-lab com>
Date: Sat, 26 Oct 2013 04:10:58 +0200

Document Title:
Paypal Inc Bug Bounty #104 - Persistent Exception Vulnerability

References (Source):

PayPal Security UID: gJ1127yy

Release Date:

Vulnerability Laboratory ID (VL-ID):

Common Vulnerability Scoring System:

Product & Service Introduction:
PayPal is a global e-commerce business allowing payments and money transfers to be made through the Internet. Online 
transfers serve as electronic alternatives to paying with traditional paper methods, such as checks and money orders. 
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 
spending limit. After that point, PayPal will attempt to take funds for a purchase from funding sources according to a 
funding hierarchy. If you set one of the funding sources as Primary, it will default to that, within that level of the 
(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 
funding source) (It can bypass the Balance); a verified bank account; other funding sources, such as non-PayPal credit 
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 persistent input validation vulnerability  in the official 
PayPal Inc (Core & API) Shipping Application.

Vulnerability Disclosure Timeline:
2013-07-31:     Researcher Notification & Coordination (Benjamin Kunz Mejri)
2013-08-01:     Vendor Notification (PayPal Site Security Team - Bug Bounty Program)
2013-09-26:     Vendor Response/Feedback (PayPal Site Security Team - Bug Bounty Program)
2013-10-25:     Vendor Fix/Patch (PayPal Site Developer Team)
2013-10-26:     Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Affected Product(s):
PayPal Inc
Product: Shipping & MOS Application - API 2013 Q2

Exploitation Technique:

Severity Level:

Technical Details & Description:
A persistent input validation web vulnerability is detected in the official PayPal Inc (Core & API) Shipping Web 
The vulnerability allows remote attacker to inject own malicious script codes to the application-side with persistent 
attack vector. 

The vulnerability is located in the service unavailable exception of the Get Started with paypal module. Remote 
attackers can request 
the Get Started service with an invalid response to display the service unavailable exception. After the provoke of the 
it is possible to execute the malicious context without secure encode. The remote attacker is able to inject script 
code to the pickup address.
The server save the input and validate it. The result is an internal server error when processing to request via POST 
method. The response of 
the internal server error exception displays the value of the stored input as output in the error. The remote attacker 
can inject the malicious 
own script code in the Scheduling a Carrier Pickup module.

Exploitation of the persistent web vulnerability requires a low privilege web application user account and low user 
Successful exploitation of the vulnerability results in session hijacking, persistent phishing, persistent external 
persistent load of malicous script codes or persistent web module context manipulation.

Vulnerable Service(s):
                                [+] Paypal Inc - Shipping Application (Core & API) 

Vulnerable Module(s):
                                [+] Get Started

Vulnerable Parameter(s):
                                [+] UnavailableAddress

Affected Module(s):
                                [+] Get Started Listing - Service Unavailable (Exception)

Proof of Concept (PoC):
The persistent input validation web vulnerability can be exploited by remote attackers with low privilege web 
application user account 
and low user interaction. For demonstration or reproduce ...

--- Exception Log ---
Service unavailable:
PayPal MultiOrder Shipping has experienced an Internal Error. CAL: caa2b9a811b2f 
PayPal MultiOrder Shipping is currently unavailable ...

Pickup Address:
"/>a%20/>"> a%20/>">


Galveston"/>, TX 77550

-- Module Text Log ---
Carrier Pickup™
Scheduling a Carrier Pickup™ is simple and can be made in the MultiOrder Shipping tool from your Ship From 
Address free of charge, regardless of the number of packages you’re sending. Your carrier will pick up your 
package by arranging a date and time with you, most likely when your mail is delivered. A US Postal Service 
carrier will validate your pickup.

--- Vulnerable Modules ---
Carrier Pickup™ Rules > Carrier Pickup™ > Schedule > Details Box (Right)
Schedule > Schedule a Shipment pickup

PoC: Exception Handling - Service UnavailableAddress

<td valign="top" width="30"><img src="pickup_data/error.gif"></td>
<td><strong>Service unavailable:</strong>
<div id="UnvailableErrorMsg">PayPal MultiOrder Shipping has 
experienced an Internal Error.  CAL: a8348eaee9327 PayPal MultiOrder 
Shipping is currently unavailable</div>
<strong>Pickup Address:</strong><br>
<span id="UnavailableAddress">"/>a%20/>"><img src="pickup_data/t.htm" onerror="prompt(document.cookie)">  
a%20/>"><h1>alsfkjlan</h1><br>a%20/>"><h1>alsfkjlan</h1><br>Galveston"/>, TX 77550<br>5305352131</span>

--- Session Cookie Log ---
shipping%252Flanding%253A%253A_flow%257E%255B1%255D%3B%20 s_sq%3D%3B; s_pers=%20s_fid%3D433059AB3DFCB070-

Manual steps to reproduce the persistent remote vulnerability ...

1. Register a paypal.com account
2. Activate the shipping module (eu users only) < we used  Current View: USPS United States
3. Login to you account and go to the shipping module
4. Open the account settings in the shipping application and include as Pickup Address the own poc as payload with 
non-malicious script code
Note: The input must be send with invalid values character like ' -: ." to let an exception popup at the end.
5. Save the data and go to the shipping application
6. We shortly log out and login again with the same user account for proof
7. Now a box popup (Get Started) when the user is processing to login > click Schedule > Schedule Pickup Carrier
8. The USPS Carrier Pickup opens and executes the injected script code (payload) as persistent bug
Note: The module displays the not secure parsed/encoded input of the pickup address in the UnavailableAddres 
exception-handling module.
9. Successful reproduced!
Note: Even if the context of the request is invalid the data will be stored and visible in the details and profile 
after usage.

Solution - Fix & Patch:
The vulnerability can be patched by a secure parse and encode of the pickupadress input fields.
To fix the second bug parse the UnavailableAddress  (output) value in the exception-handling.

Security Risk:
The security risk of the persistent input validation and exception-handling vulnerability is estimated as medium(+).

Credits & Authors:
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm () evolution-sec com)

Disclaimer & Information:
The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all 
either expressed or implied, including the warranties of merchantability and capability for a particular purpose. 
Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss 
of business 
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 
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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