PayPal Inc Bug Bounty #113 – CS Cross Site Vulnerability

Document Title:
PayPal Inc Bug Bounty #113 – CS Cross Site 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: []

Abstract Advisory Information:
An independent Vulnerability Laboratory researcher discovered a client-side cross site scripting web vulnerability in the official PayPal Inc online service web-application.

Vulnerability Disclosure Timeline:
2014-12-30: Researcher Notification & Coordination (Milan A Solanki)
2014-12-31: Vendor Notification (PayPal Inc – Bug Bounty Team)
2015-01-08: Vendor Response/Feedback (PayPal Inc – Bug Bounty Team)
2015-01-15: Vendor Fix/Patch (PayPal Inc – Developer Team)
2015-04-18: Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Affected Product(s):
PayPal Inc
Product: PayPal – Online Service Web Application 2015 Q2

Exploitation Technique:

Severity Level:

Technical Details & Description:
A non persistent cross site scripting web vulnerability has been discovered in the official PayPal Inc online service web-application.
The vulnerability allows remote attackers to hijack website customer, moderator or admin sessions data by client-side manipulated cross site requests.

The vulnerability is located in the `q` values of the merchant search module. Remote attackers are able to inject own script codes to the vulnerable GET method
request of the merchant search module. The attack vector of the vulnerability is located on the client-side of the paypal online service web-application.
The request method to inject the script code on client-side is `GET`. The injection point of the issue is the vulnerable `q` value in the search engine and
the script code execution point is located in the results output context page.

The security risk of the non-persistent input validation web vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 3.4.
Exploitation of the client-side cross site scripting web vulnerability requires low user interaction (click) and no privileged application user account.
Successful exploitation results in client-side account theft by hijacking, client-side phishing, client-side external redirects and non-persistent manipulation
of affected or connected service modules.

Request Method(s):
[+] GET

Vulnerable Service(s):
[+] PayPal Inc (

Vulnerable Module(s):
[+] Merchant Search

Vulnerable Parameter(s):
[+] q

Affected Section(s):
[+] Merchant Search Results

Proof of Concept (PoC):
The client-side cross site scripting web vulnerability can be exploited by remote attackers without privileged application user account and with low user interaction (click).
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.


PoC: Payload(s)


Solution – Fix & Patch:
2015-01-15: Vendor Fix/Patch (PayPal Inc – Developer Team)

Security Risk:
The security risk of the client-side cross site scripting web vulnerability in the `q` merchant search value is estimated as medium. (CVSS 3.4)

Credits & Authors:
Milan A Solanki – ( []

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