PayPal Inc #168 - Insufficient Authentication Vulnerability

Document Title:
===============
PayPal Inc #168 - Insufficient Authentication Vulnerability


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=2091


Release Date:
=============
2017-10-30


Vulnerability Laboratory ID (VL-ID):
====================================
2091


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


Vulnerability Class:
====================
Enumeration


Current Estimated Price:
========================
500€ - 1.000€


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.

(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:
==================================
2017-08-28: Researcher Notification & Coordination (Core Security Researcher)
2017-08-29: Vendor Notification (PayPal Inc Security Department)
2017-09-05: Vendor Response/Feedback (PayPal Inc Security Department)
2017-10-20: Vendor Fix/Patch (PayPal Inc Service Developer Team)
2017-10-29: Security Acknowledgements (PayPal Inc Security Department)
2017-10-30: Public Disclosure (Vulnerability Laboratory)


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


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

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):
[+] POST

Vulnerable Module(s):
[+] signup business account

Affected Module(s):
[+] email verification redirect


Proof of Concept (PoC):
=======================
The security issue can be exploited by remote attackers without privileged user account 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 sign up business account which uses the email to check

Example: (URL - Request) 
https://www.paypal.com/bizsignup/flows/americas/standard/check-account-existence

email[value]:[email protected]
email[isValidated]:true
pageName:checkAccount
pageCompletions[checkAccount]:false
pageCompletions[createPassword]:false
pageCompletions[create]:false
pageCompletions[businessInfo]:false
pageCompletions[personalInfo]:false
pageCompletions[upgradeBusinessAccount]:false

Redirect : https://www.paypal.com/bizsignup/#/createPassword << means account not exist 
Redirect : https://www.paypal.com/signin?country.x=US&locale.x=en_US << account exist

Note: A simple redirect check can be used to enumerate user account emails of paypal


Solution - Fix & Patch:
=======================
The vulnerability can be patched by approval of the authentication in the marketing application to add some brute force protection (example: captcha).


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:
==================
Vulnerability Laboratory [Research Team] Chamli [[email protected]] - https://www.vulnerability-lab.com/show.php?user=Chamli


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=========================
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