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Paypal Inc Bug Bounty #30 - Filter Bypass & Persistent Vulnerabilities

2014-10-06 12:00
Document Title:
===============
Paypal Inc Bug Bounty #30 - Filter Bypass & Persistent Vulnerabilities


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=705


Release Date:
=============
2014-09-26


Vulnerability Laboratory ID (VL-ID):
====================================
705


Common Vulnerability Scoring System:
====================================
4.3


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


Abstract Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered multiple web vulnerabilities in the official PayPal Here mobile
notify me online service web-application.


Vulnerability Disclosure Timeline:
==================================
2014-09-26: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================

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


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


Technical Details & Description:
================================
2 persistent POST Inject Vulnerabilities has been discovered in the official PayPal Here mobile Notify Me online
service web-application.
The vulnerability allows remote attackers to inject own malicious script code on the application-side of the vulnerable
web function.

The first 2 vulnerabilities are located in the `first_name` and `last_name` values of the `Notify Me` online service
web-application.
Remote attacker are able to inject own malicious script codes in the firstname and lastname values of the Notify Me
send POST method request.
The execution of the injected script code occurs in the `biz.paypal` notify mail that arrives after the successful POST
method request of the
paypal api and web-application. The context execution is located in the mail header next to the introduction to the
paypal customer.

A input filter validation bypass vulnerability has been discovered in the official PayPal Here mobile Notify Me online
service web-application.
To inject the values the attacker needs to use a session tamper to interact.

During the pentests the input fields disallows to insert of script codes (firstname & lastname). We tried to manipulate
the POST request which
is not connected to the input validation form (after a first load) with own malicious test values. The result was the
successful execution of
the malicious test code in the paypal notify me service mail. The protection of the input was not connected to the
session request which results
in a successful bypass by manipulation of the post values after the first web request.

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 web vulnerability requires no privileged web-application user account but low or
medium user interaction.
Successful exploitation of the vulnerabilities result in persistent phishing mails, session hijacking, persistent
external redirect to malicious
sources and application-side manipulation of affected or connected module context.

Request Method(s):
[+] POST

Vulnerable Module(s):
[+] PayPal Here - Notify Me

Vulnerable Input Field(s):
[+] Firstname
[+] Lastname

Vulnerable Parameter(s):
[+] first_name
[+] last_name

Affected Module(s):
[+] Notification Mail - You’re in line to get PayPal Here™


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

Manual steps to reproduce the application-side vulnerability ...

1. Open the paypal.com website and surf to the notify me service application site
(https://www.paypal.com/webapps/mpp/credit-card-reader)
2. Include your email and the random company name, firstname and lastname as regular (Do not save to notify yet!)
3. Start a session tamper to manipulate the request after the first attempt
4. Change the vulnerable firstname and lastname values with own script code payloads and continue to intercept the
request
5. Open your mailbox and review the arrived paypal inc notify me service mail of the website formular
6. The persistent execution occurs in the header location next to the paypal customer introduction word `Dear
[First-&Lastname]`
Note: The attacker is now able to manipulate the complete mail body and header of the notify me context to compromise
other user accounts
7. Successful reproduce of the remote vulnerability!


PoC: Notification Mail - Firstname & Lastname

<td style="font-family:verdana,sans-serif; font-size:13px; color:rgb(54, 54, 54);
text-align:left; "><div class="mktEditable" id="copy"><p><br><span style="font-family: arial,helvetica,sans-serif;
font-size: 12px;">Dear svenja "><[PERSISTENT INJECET SCRIPT CODE! FIRSTNAME & LASTNAME];)" <, <="" span=""></p>
<p><span style="font-family: arial,helvetica,sans-serif; font-size: 12px;">
Thank you for your interest in PayPal Here! You are now a confirmed member of the PayPal Here “
Exclusive Release” wait list.
PayPal Here will be available shortly and you will be notified with instructions on how to get your free mobile
card reader and access to the app through iTunes or the Android Market (Play).</span></p>
<p><span style="font-family: arial,helvetica,sans-serif; font-size: 12px;">PayPal Here will make a big difference to
your business.
Instead of chasing payments or missing out on sales, you’ll be able to plug the card reader into your smart
phone and get paid on the spot. </span></p>


--- PoC Session Logs [POST] ---
POST (Request): Standard
oid=00D300000000LaY
ret
URL=https%3A%2F%2Fwww.paypal.com%2Fwebapps%2Fmpp%2Fcredit-card-reader-thank-you
lead_source=Web-KNLBSTR
recordType=012800000003bgg
Campaign_ID=70180000000MGgf
email=bkm () evolution-sec com
first_name=Benjamin
last_name=KunzMejri
mobile=01776713371337
url=http%3A%2F%2Fwww.vulnerability-lab.com
company=vulnerabilitylab
Additional_Services__c=Android

POST (Request): Manipulated
oid=00D300000000LaY
ret
URL=https%3A%2F%2Fwww.paypal.com%2Fwebapps%2Fmpp%2Fcredit-card-reader-thank-you
lead_source=Web-KNLBSTR
recordType=012800000003bgg
Campaign_ID=70180000000MGgf
email=bkm () evolution-sec com
first_name=<[PERSISTENT INJECTED SCRIPT CODE! #1]>
last_name="><[PERSISTENT INJECTED SCRIPT CODE! #1]<
mobile=01776713371337
url=http%3A%2F%2Fwww.vulnerability-lab.com
company=vulnerabilitylab
Additional_Services__c=1337kungfu_0ne


Reference(s):
https://www.paypal.com/webapps/mpp/credit-card-reader
https%3A%2F%2Fwww.paypal.com%2Fwebapps%2Fmpp%2Fcredit-card-reader-thank-you


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure encode and parse of the firstname and lastname values in the notify me
POST method request.
Restrict the notify me input fields and disallow special chars. Parse the in the outgoing mail context the names that
are stored in the
dbms to prevent further script code executions. Connect a token to the session to prepare exceptions that prevent
malicious interaction.


Security Risk:
==============
The security risk of the two persistent input validation vulnerabilities via POST method request are estimated as
medium.
The security risk of the filter bypass vulnerability e in the paypal inc notify me form is estimated as medium.


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


Disclaimer & Information:
=========================
The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all
warranties, either
expressed or implied, including the warranties of merchantability and capability for a particular purpose.
Vulnerability-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 limitation 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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Source: 32/tcO/4102/erusolcsidlluf/gro.stsilces

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