Message-ID: <55F2B468.3070106@vulnerability-lab.com>
Date: Fri, 11 Sep 2015 13:00:56 +0200
From: Vulnerability Lab <research@...nerability-lab.com>
To: fulldisclosure@...lists.org
Subject: [FD] PayPal Inc - Security Approval & 2FA Session Auth Bypass (API)
 Vulnerability

Document Title:
===============
PayPal Inc - Security Approval & 2FA Session Auth Bypass (API) Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1486

Video: http://www.vulnerability-lab.com/get_content.php?id=1485

Watch Video: https://www.youtube.com/watch?v=Gzq8TD2Co9Y

EIBBP-31865

Vulnerability Magazine: http://magazine.vulnerability-db.com/?q=articles/2015/07/20/paypal-inc-identity-check-restriction-bypass-vulnerability


http://www.theregister.co.uk/2015/09/04/paypal_bug_brace_xss_2fa_bypass/
http://www.securityweek.com/paypal-mobile-apps-plagued-authentication-flaw-researcher
http://news.softpedia.com/news/infosec-researcher-bypasses-paypal-authentication-system-on-its-mobile-apps-491135.shtml
http://securityaffairs.co/wordpress/39951/hacking/authentication-paypal-mobile-app.html
http://news.hitb.org/content/paypal-mobile-apps-plagued-authentication-f...


Release Date:
=============
2015-09-02


Vulnerability Laboratory ID (VL-ID):
====================================
1486


Common Vulnerability Scoring System:
====================================
6.1


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 Core Research Team discovered a restriction filter bypass in the official PayPal Inc Mobile API for Apple iOS.


Vulnerability Disclosure Timeline:
==================================
2015-04-30: Researcher Notification & Coordination (Benjamin Kunz Mejri - Evolution Security GmbH)
2015-05-02: Vendor Notification (PayPal Inc - Security & Bug Bounty Team)
2015-05-13: Vendor Response/Feedback (PayPal Inc - Security & Bug Bounty Team)
2015-**-**: Vendor Fix/Patch (PayPal Inc - Developer Team)
2015-09-02: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
PayPal Inc
Product: Mobile Web Application (API) 2015 Q2


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


Severity Level:
===============
High


Technical Details & Description:
================================
By processing multiple login we saw a bug in the mobile app api next to the identity check. Normally an user account logs in and if the account is restricted by 
several requests a stable form popup to call paypal or write a ticket mail.

By processing to request the form multiple times with an existing account (x01445@...il.com:chaos666) we was able to bypass 
the auth verification check to approve the account owner.

The api loads the website context and the user is able to include inside of the identity check with a browser engine the own user account. 
Even if the account is restricted the user can access via mobile api with the exisiting cookies.

The security identity check to approve has been included to verify that no user logs in to unauthorized- or restricted accounts.
In that case we demonstrate in the video how we bypass the validation and how it should look normally with the final request.


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

The video demonstrates a flaw inside of the mobile app api that redirects an user account with restricted credentials inside of the app 
to the original website source.
The cookies authorize the account to login even if the regular portal denies it because of the identity approval.
The issue is not connected to the 6 month ago reported restriction bypass and reveals a signifanct risk to user accounts because of fraud and account theft.

The video deomstrates a security bug in the official paypal mobile ios api. The bug allows to bypas the account restriction by usage of a validation flaw inside of the service.
The identity check approves restricted user accounts. In the first released issue we demonstrated how to bypass the auth. In case of the new issue 
the researcher demonstrates how to bypass the identity check that approves the paypal account. The attacker bypass the validation by multiple 
requests and dumps the real website for login inside the app with cookies and co.

Video Demonstration: https://www.youtube.com/watch?v=Gzq8TD2Co9Y


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure redirect of a multi requesting source to the main mobile api. Disallow to load the website context with the app cookies 
after a successful login through a restricted account to prevent.


Security Risk:
==============
The security risk of the remote  mobile api  identity approval check bypass is estimated as high. (CVSS 6.1)


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm@...lution-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 
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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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