CMSimple 5.15 - Remote Code Execution (Authenticated) Vulnerability

# Exploit Title: CMSimple 5.15 - Remote Command Execution
# Exploit Author: Ahmet Ümit BAYRAM
# Vendor Homepage: https://www.cmsimple.org
# Software Link: https://www.cmsimple.org/downloads_cmsimple50/CMSimple_5-15.zip
# Version: latest
# Tested on: MacOS

# Log in to SimpleCMS.
# Go to Settings > CMS
# Append ",php" to the end of the Extensions_userfiles field and save it.
# Navigate to Files > Media
# Select and upload shell.php
# Your shell is ready: https://{url}/userfiles/media/shell.php