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[Full-disclosure] PayPal Bug Bounty #45 BillSafe - Remote Auth Bypass Session Web Vulnerability

Title:
======
PayPal Bug Bounty #45 BillSafe - Remote Auth Bypass Session Web Vulnerability


Date:
=====
2013-04-30


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=804
http://www.vulnerability-lab.com/dev/?p=665

PayPal Security UID:    og1eb1mgi

PayPal Inc Bug Bounty:  5000$ (USD)


VL-ID:
=====
804


Common Vulnerability Scoring System:
====================================
8.6


Introduction:
=============
Als spezialisierte Factoringgesellschaft für die Abwicklung von 
Rechnungskauf-Zahlungen im Internet wurde die BillSAFE GmbH 2008 
durch die Altgesellschafter der mediafinanz AG gegründet. Das Management der 
BillSAFE GmbH besteht ausnahmslos aus Risikomanagement-Experten 
mit jahrelanger Erfahrung aus der Betreuung von namhaften Online-Shops und 
Versandhandelsunternehmen. 

2009 erfolgte die reguläre Inbetriebnahme des Services mit der Anbindung der 
ersten 100 Online-Shops. 2010 beteiligte sich die eBay Tochter PayPal 
im Rahmen einer strategischen Partnerschaft an der BillSAFE GmbH. 2011 wurde 
ein neuer Unternehmensstandort auf dem eBay Campus in Berlin Dreilinden 
eröffnet, um die enge operative Zusammenarbeit mit PayPal weiter zu 
intensivieren. Seit Dezember 2011 ist die BillSAFE GmbH ein 100%iges PayPal 
Unternehmen und Teil der eBay Firmengruppe. Die von BillSAFE angebotenen 
Produkte bündeln die Erfahrung aus der Abwicklung von mehreren hundert 
Millionen E-Commerce Transaktionen durch PayPal mit der Expertise in der 
Bearbeitung von mehreren Millionen Inkassofällen durch die mediafinanz AG.

(Copy of the Vendor Homepage: http://www.billsafe.de/company/about )


Abstract:
=========
The Vulnerabilitly Laboratory Research Team discovered a auth bypass 
vulnerability in Paypals Billsafe online payment service web application.


Report-Timeline:
================
2013-01-27:     Researcher Notification & Coordination
2013-01-28:     Vendor Notification
2013-02-12:     Vendor Response/Feedback
2013-04-03:     Vendor Fix/Patch
2013-04-30:     Public Disclosure


Status:
========
Published


Affected Products:
==================
PayPal Inc
Product: BillSafe - Online Payment Service 2013 Q1


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


Severity:
=========
Critical


Details:
========
A auth bypass web session vulnerability is detected  in Paypals Billsafe online 
payment service web application.
The vulnerability typus allows an attacker to bypass the first login user 
session auth and change passwords and 
emails of billsafe web application accounts. 

The application is processing to request after a account activation plain 
passwords without any kind of token 
protection mechanism. The vulnerability is located in the first login section 
of the billsafe website when 
processing to load (after the activation) manipulated user/email/pass context. 
Remote attackers can manipulate 
accounts by live tampering the activation session link request. When the remote 
attacker is tampering the session 
live, he only needs to exchange the plain requested values (name/email/pass) 
with the earlier valid requested values.
After changing the vulnerable values the attacker only needs to send the same 
request again to reset 
any billsafe client application account.

Exploitation of the vulnerability requires no privileged application user 
account and no user interaction.
Successful exploitation of the vulnerability results in account compromise, 
account manipulation and account theaft.


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

Vulnerable Module(s):
                                [+] Account - First Login

Vulnerable Parameter(s):
                                [+] eMail
                                [+] password 

Affected Module(s):
                                [+] Account System


Proof of Concept:
=================
The auth bypass vulnerability can be exploited by remote attackers without 
required user interaction or privileged application user account.
For demonstration or reproduce ...

Requirement(s):
                                [+] Browser (Mozilla)
                                [+] Tamper Data - Addon
                                [+] A secound valid registration session change 
values


Registration(s):
http://client.billsafe.de/login/register/id/aa3a863357fe6acb0fe16f7cce1a46d135235

Host=client.billsafe.de
User-Agent=Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20100101 
Firefox/17.0
Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language=de-de,de;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding=gzip, deflate
DNT=1
Connection=keep-alive
Referer=http://client.billsafe.de/login/first-login/
Cookie=__utma=22145316.759281629.1356643963.1356643963.1356653145.2; 
__utmc=22145316; 
__utmz=22145316.1356643963.1.1.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=billsafe%20paypal;
 
PHPSESSID=mdkgkm8j91n4d57hdl8c9bjqo6; __utmb=22145316.96.9.1356654870355

Cache-Control=max-age=0
Content-Type=application/x-www-form-urlencoded
Content-Length=92

POSTDATA=clientId=35235&password=benjamin337&email=bkm%40vulnerability-lab.com&integration=prepared


Reference(s):
http://client.billsafe.de/login/first-login/


Manually steps to reproduce ...
1. Start your web browser and open up the billsafe website
2. Register an user account via the main registration form
3. Go to your postbox and copy the link with the session
4. Open the browser, start tamper data and load the request (mail link) of the 
login register id
5. The tamper will show you the plain context which can be changed to your own 
values
6. Hold the request and change the values to your own new email account or 
password
7. Reload the page, change to your own new password, load the mail
8. Registration successful. You can now login with the account details of any 
other user.


Solution:
=========
2013-04-03:     Vendor Fix/Patch by PayPal Inc coordinated via the PayPal Site 
Security Team
Coordination:   Security Case Manager (Jack)

Risk:
=====
The security risk of the auth bypass session web vulnerability is estimated as 
critical.


Credits:
========
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri 
(bkm@xxxxxxxxxxxxxxxxxxxxx)


Disclaimer:
===========
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 in any case of damage, including direct, 
indirect, incidental, consequential loss of business 
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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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