PayPal Inc Bug Bounty #42 - Persistent POST Inject Vulnerability

From: Vulnerability Lab <>
Subject: PayPal Inc Bug Bounty #42 - Persistent POST Inject Vulnerability

Document Title:
PayPal Inc Bug Bounty #42 - Persistent POST Inject Vulnerability

References (Source):

PayPal Security UID: kxy1ea5ech

Release Date:

Vulnerability Laboratory ID (VL-ID):

Common Vulnerability Scoring System:

Product & Service Introduction:
Als spezialisierte Factoringgesellschaft fr die Abwicklung von Rechnungskauf-Zahlungen im Internet wurde die BillSAFE GmbH 2008 
durch die Altgesellschafter der mediafinanz AG gegrndet. 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 regulre 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 
erffnet, 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 bndeln die Erfahrung aus der Abwicklung von mehreren hundert 
Millionen E-Commerce Transaktionen durch PayPal mit der Expertise in der Bearbeitung von mehreren Millionen Inkassofllen durch die mediafinanz AG.

(Copy of the Vendor Homepage: )

Abstract Advisory Information:
The Vulnerability Laboratory Research Team discovered a POST inject web vulnerability  in the official Paypal Inc Billsafe online payment service web-application.

Vulnerability Disclosure Timeline:
2012-12-27:        Researcher Notification & Coordination (Benjamin Kunz Mejri)
2013-12-28:       Vendor Notification (PayPal Site Security Team - Bug Bounty Program)
2013-01-04:    Vendor Response/Feedback (PayPal Site Security Team - Bug Bounty Program)
2013-11-15:       Vendor Fix/Patch (PayPal Developer Team - Bug Bounty Reward)
2013-11-16:    Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Affected Product(s):
PayPal Inc
Product: BillSafe - Online Payment Service 2012 Q4

Exploitation Technique:

Severity Level:

Technical Details & Description:
A remote POST inject web vulnerability has been discovered in the official Paypal Inc Billsafe online payment service web-application.
The issue allows remote attackers to inject via POST method request own malicious persistent script codes to compromise the application.

The vulnerability is located in the integration center module. Remote attackers can manipulate the POST method request of the 
vulnerable `Register to download formular`. The vulnerable application values are company (firma), `firstname (vorname), 
`lastname (nachname)` and `shop-url`. The server accepts the manipulated POST context and saves all details as html in the 
application dbms for future usage. The security risk of the POST inject web vulnerability with persistent attack vector is 
estimated medium with a cvss (common vulnerability scoring system) count of 3.5(+). 

The input does not validate the saved context and the input fields are not restricted to prevent future executions. 
Whenever an attacker is processing to include malicious context the request via POST method will be accepted by the 
server without secure encoding procedure.

Exploitation of the POST inject web vulnerability requires no privileged web application user account and low or medium user interaction. 
Successful exploitation of the client-side cross site scripting web vulnerabilities results in session hijacking, client-side phishing, 
client-side unauthorized/open (external) redirects and client-side manipulation of the exception module context.

Vulnerable Service(s):
                            [+] Paypal - BillSafe

Vulnerable Section(s):
                              [+] Integration Center (Integrations Center)

Vulnerable Module(s):
                                [+] Register to download Formular (Registration zum Formular download)

Vulnerable Parameter(s):
                           [+] Firma (company)
                                [+] Vorname (firstname)
                            [+] Nachname (lastname)
                            [+] Shop-URL 

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

--- PoC Session Request Logs [POST] ---
User-Agent=Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20100101 Firefox/17.0
Accept=text/html, */*; q=0.01
Accept-Encoding=gzip, deflate
Content-Type=application/x-www-form-urlencoded; charset=UTF-8

company=%3E%22+'[INJECTED SCRIPT CODE!])+%3C&firstname=%3E%22+'[INJECTED SCRIPT CODE!])+%3C&lastname=%3E%22+'[INJECTED SCRIPT CODE!])

--- Response Header [200] ---
Status=OK - 200
Date=Thu, 27 Dec 2012 21:47:11 GMT
Expires=Sat, 26 Jan 2013 21:47:11 GMT
Keep-Alive=timeout=15, max=68

Reference(s): > [Download] > [Download]

Solution - Fix & Patch:
The vulnerability can be patched by a secure parse of the vulnerable values in the POST method request.
Also encode and parse the output of the vulnerable values even if the input has already been encoded and restricted.

Security Risk:
The security risk of the POST inject web vulnerability in the register to download formular module is estimated as medium.

Credits & Authors:
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ( []

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