Paypal Bug Bounty #14 - Persistent Payment Mail Encoding Vulnerability Nov 20 2013 04:08AM
Vulnerability Lab (research vulnerability-lab com)
Document Title:
Paypal Inc BB #14 - Persistent Payment Mail Vulnerability

References (Source):

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 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.

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

Abstract Advisory Information:
The Vulnerability Laboratory Research Team discovered a Web Vulnerability in the official Paypal ecommerce website application.

Vulnerability Disclosure Timeline:
2012-07-07: Researcher Notification & Coordination (Benjamin Kunz Mejri)
2012-07-10: Vendor Notification (PayPal Site Security Team - Bug Bounty Program)
2013-03-07: Vendor Response/Feedback (PayPal Site Security Team - Bug Bounty Program)
2012-11-01: Vendor Fix/Patch (PayPal Inc Developer Team - Bug Bounty Reward $$$)
2012-11-20: Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Exploitation Technique:

Severity Level:

Technical Details & Description:
A persistent input validation vulnerability has been discovered in the official Paypal Inc website content management system & API.
The bug allows remote attackers to inject own malicious script codes to the application-side of the paypal online-service.

The vulnerability is located in the vulnerable `From` value of the Unclaimed Payments > Phone Payments (unconfirmed phone numbers) module.
The script code execute occurs in the important `Phone Payments` request list of the verify a receiver via phonenumber function.
The security risk of the persistent web vulnerabilities in the payments module is estimated as high with a cvss (common vulnerability
scoring system) count of 5.1(+)|(-)5.2.

The vulnerability can be exploited by remote attackers with low user inter action and low privileged paypal customer/pro/seller account.
Successful exploitation of the vulnerability results in session hijacking (customers), account steal via persistent injects (listing),
persistent phishing or persistent manipulation of module- or connected module context.

Request Method(s):
[+] POST

Vulnerable Type(s):
[+] Customer/Pro/Seller Accounts

Vulnerable Section(s):
[+] Unclaimed Payments

Vulnerable Module(s):
[+] Phone Payments

Vulnerable Parameter(s):
[+] From

Proof of Concept (PoC):
The persistent input validation web vulnerability can be exploited by remote attackers with low privileged paypal customer/pro/seller account
& low user inter action. For security demonstration or to reproduce the vulnerability follow the provided information below.

PoC: Money Request Mail Notification

<tbody><tr class="tableRowLightBlue"><td class="tableCellRegularSmall" colspan="2"><span class="emphasis">
To</span></td><td> <span class="emphasis">From</span></td><td class="tableCellRegularSmall"><span class="emphasis">
Amount</span> </td><td class="tableCellRegularSmall"> <span class="emphasis">Date Sent</span></td>
<td class="tableCellRegularSmall"> <span class="emphasis">Status</span></td></tr><tr><td class="tableCellRegularSmall">
<input name="phone_id" value="YbLGqPsRLZzdGAWnePuHErCuqMFSQXIxVdN33JaVMbXUnWvlp5_5H7Ju8R6LaZplC
o7kApCTs3TNf0ol" type="radio">
</td><td class="tableCellRegularSmall"> 408-678-0945</td><td class="tableCellRegularSmall"> Danh Nguyen's Test Store</td>
<td class="tableCellRegularSmall">$1333337.00 USD </td><td class="tableCellRegularSmall"> Dec 3, 2010</td>
<td class="tableCellRegularSmall"> Pending</td></tr><tr><td class="tableCellRegularSmall">
<input name="phone_id" value="32vLCA4HtsQRr2cQEYpHcCf5wYT0V0kKrp4JnOSqkl78hb2qEUj3A8WvEssI1RqiR
Tyx3VM8chWSogB0" type="radio"></td>
<td class="tableCellRegularSmall"> 408-983-5678</td>
<td class="tableCellRegularSmall"> "><[PERSISTENT INJECTED SCRIPT CODE!]"> <</td><td
class="tableCellRegularSmall">$50.00 USD </td><td

POC URL1: https://www.paypal.com/us/cgi-bin/webscr?cmd=_unconfirmed-payments
POC URL2: https://www.sandbox.paypal.com/us/cgi-bin/webscr?cmd=_unconfirmed-paymen

Solution - Fix & Patch:
The vulnerability can be patched by a secure encode and parse of the vulnerable From (phone_id) application value.

Step 1: Encode and restrict the vulnerable input fields
Step 2: Parse & filter the stored context when processing to reload as affected output

Security Risk:
The security risk of the persistent script code inject vulnerability is estimated as high(-).

Credits & Authors:
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm (at) vulnerability-lab (dot) com [email concealed])

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