Grav CMS 1.4.2 Admin Plugin - Cross-Site Scripting

# Exploit Title: GravCMS Core (Admin Plugin) v1.4.2 - Persistent Cross-Site Scripting
# Date: 2017-06-07
# Exploit Author: Ahsan Tahir
# Vendor Homepage: https://getgrav.org/
# Software Link: https://getgrav.org/download/core/grav-admin/1.2.4
# Version: 1.4.2
# Tested on: [Kali Linux 2.0 | Windows 8.1]
# Email: [email protected]
# Contact: https://twitter.com/AhsanTahirAT

Release Date:
=============
2017-06-07


Product & Service Introduction:
===============================
Grav is built and maintained by a team of dedicated and passionate developers, designers and users. 
As Grav is an open source project we greatly appreciate user contribution and commitment. These are the key folks that make this all possible.


Abstract Advisory Information:
==============================
Ahsan Tahir, an independent vulnerability researcher discovered a Persistent Cross-Site Scripting Vulnerability in GravCMS Admin Plugin (v 1.4.2)


Vulnerability Disclosure Timeline:
==================================
2017-06-07: Found the vulnerability.
2017-06-07: Reported to vendor.
2017-06-07: Published.

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


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


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


Technical Details & Description:
================================
The security risk of the xss vulnerability is estimated as medium with a common vulnerability scoring system count of 3.6. 
Exploitation of the persistent xss web vulnerability requires a limited admin 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.


Proof of Concept (PoC):
=======================
The persistent input validation vulnerability can be exploited by restricted user accounts with low user interaction.
For security demonstraton or to reproduce the vulnerability follow the provided information and steps below to continue.

Payload (Exploitation): [Click Me](javascript:alert(1))

[+] Manual steps to reproduce ..
1. Login with the admin or editor account in GravCMS
2. Go to edit page option (e.g http://127.0.0.1/cms/grav-admin/admin/pages/home)
3. Put the payload "[Click Me](javascript:alert(1))" (without quotes) in the content of page
4. Save Page!
5. Go to the index page (e.g http://127.0.0.1/cms/grav-admin/)
6. Click on "Click Me"
7. The Javascript execution occurs - Successful reproduce of the persistent cross site scripting vulnerability!


Credits & Authors:
==================
Ahsan Tahir - [https://twitter.com/AhsanTahirAT]