Title:
======
Paypal Bug Bounty #17 - Persistent Web Vulnerability


Date:
=====
2013-01-28


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=671

PayPal UID: tlm30fdsh


VL-ID:
=====
671


Common Vulnerability Scoring System:
====================================
3


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:
=========
The Vulnerability Laboratory Research Team discovered a persistent web vulnerability in the official Paypal ecommerce website application.


Report-Timeline:
================
2012-07-30:  Researcher Notification & Coordination
2012-07-31:  Vendor Notification
2012-08-09:  Vendor Response/Feedback
2013-01-14:  Vendor Fix/Patch
2013-01-28:  Public or Non-Public Disclosure


Status:
========
Published


Affected Products:
==================

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


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


Details:
========
A persistent input validation vulnerability is detected in the official Paypal website application (Customer/Pro/Seller).
The bug allows an attacker (remote) to implement/inject malicious script code on the application side (persistent) of 
the paypal web service. The vulnerability is located in the Zertifikatsänderung des öffentlichen Schlüssels module with 
the bound vulnerable name & id mail listing parameters. The vulnerability can be exploited by remote attackers with low 
or medium required user inter action and with privileged Customer/Pro/Seller account. Successful exploitation of the 
vulnerability can lead to persistent session hijacking (customers), account steal via persistent web attacks, persistent 
phishing or stable (persistent) certificate mail notification context manipulation.


Vulnerable Module(s):
                          [+] Zertifikatsänderung des öffentlichen Schlüssels  (Delete too!)

Vulnerable Parameter(s):
                          [+] NAME & ID

Affected Section(s):
        [+] Notification Mail


Proof of Concept:
=================
The vulnerability can be exploited by remote attackers with privileged user account and medium or high required user inter action.
For demonstration or reproduce ...


Review:  Certificate Change Notification - Username & Company

<html><head>
<title>Zertifikatsänderung des öffentlichen Schlüssels</title>
<link rel="important stylesheet" href="chrome://messagebody/skin/messageBody.css">
</head>
<body>
<table class="header-part1" border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td><b>Betreff: 
</b>Zertifikatsänderung des öffentlichen Schlüssels</td></tr><tr><td><b>Von: </b>"service@paypal.de" <service@paypal.de>
</td></tr><tr><td><b>Datum: </b>Sat, 28 Jul 2012 22:49:45 -0700</td></tr></tbody></table><table class="header-part2" border="0" 
cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td><b>An: </b>denjo <x01445@gmail.com></td></tr></tbody></table><br>
<div class="moz-text-plain"><pre wrap="">Guten Tag benjo >"<iframe src="http://vuln-lab.com">!

Hiermit informieren wir Sie darüber, dass Sie erfolgreich ein Zertifikat des öffentlichen Schlüssels mit der folgenden ID 
hinzugefügt haben: 9XG235W6L7R92.

HINWEIS: Wenn Sie kein Zertifikat des öffentlichen Schlüssels hinzufügen möchten, setzen Sie sich umgehend unter der auf der 
nächsten Seite angegebenen Rufnummer telefonisch mit uns in Verbindung:

<a class="moz-txt-link-freetext" href="https://www.paypal.com/de/contact-phone">https://www.paypal.com/de/contact-phone</a>

Herzliche Grüße
Ihr PayPal-Team



Review:  Certificate Change Notification - ID


<html><head>
<title>Zertifikatsänderung des öffentlichen Schlüssels</title>
<link rel="important stylesheet" href="chrome://messagebody/skin/messageBody.css">
</head>
<body>
<table class="header-part1" border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td>
<b>Betreff: </b>Zertifikatsänderung des öffentlichen Schlüssels</td></tr><tr><td><b>Von: </b>"service@paypal.de" 
<service@paypal.de></td></tr><tr><td><b>Datum: </b>Sat, 28 Jul 2012 22:49:45 -0700</td></tr></tbody></table>
<table class="header-part2" border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td><b>An: 
</b>denjo schenjo <x01445@gmail.com></td></tr></tbody></table><br>
<div class="moz-text-plain"><pre wrap="">Guten Tag denjo schenjo!

Hiermit informieren wir Sie darüber, dass Sie erfolgreich ein Zertifikat des öffentlichen Schlüssels mit der folgenden 
ID hinzugefügt haben: 9XG137W6L7R92>"<iframe src="http://vuln-lab.com">.

HINWEIS: Wenn Sie kein Zertifikat des öffentlichen Schlüssels hinzufügen möchten, setzen Sie sich umgehend unter der auf 
der nächsten Seite angegebenen Rufnummer telefonisch mit uns in Verbindung:

<a class="moz-txt-link-freetext" href="https://www.paypal.com/de/contact-phone">https://www.paypal.com/de/contact-phone</a>

Herzliche Grüße
Ihr PayPal-Team


Note: 
The ID notification will be send with the request of the changes. The attacker can manipulate the value by injecting via POST.
The select of the notification will be handled by the post request and not by a special request to the real existing updated 
input of the database. The result of the request notification is the execution of the persistent malicious script code out of the ID context.



Solution:
=========
2013-01-14:  Vendor Fix/Patch by PayPal Security Team


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


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


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===========
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