PayPal BillSafe Authentication Bypass

Type packetstorm
Reporter Benjamin Kunz Mejri
Modified 2013-04-29T00:00:00


PayPal Bug Bounty #45 BillSafe - Remote Auth Bypass Session Web Vulnerability  
PayPal Security UID: og1eb1mgi  
PayPal Inc Bug Bounty: 5000$ (USD)  
Common Vulnerability Scoring System:  
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: )  
The Vulnerabilitly Laboratory Research Team discovered a auth bypass vulnerability in Paypals Billsafe online payment service web application.  
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  
Affected Products:  
PayPal Inc  
Product: BillSafe - Online Payment Service 2013 Q1  
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 ...  
[+] Browser (Mozilla)  
[+] Tamper Data - Addon  
[+] A secound valid registration session change values  
User-Agent=Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20100101 Firefox/17.0  
Accept-Encoding=gzip, deflate  
Cookie=__utma=22145316.759281629.1356643963.1356643963.1356653145.2; __utmc=22145316;   
PHPSESSID=mdkgkm8j91n4d57hdl8c9bjqo6; __utmb=22145316.96.9.1356654870355  
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.  
2013-04-03: Vendor Fix/Patch by PayPal Inc coordinated via the PayPal Site Security Team  
Coordination: Security Case Manager (Jack)  
The security risk of the auth bypass session web vulnerability is estimated as critical.  
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (  
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