Drupal Security

Drupal Security

Critical Security Patterns

SQL Injection Prevention

NEVER concatenate user input into queries:

// VULNERABLE - SQL injection
$query = "SELECT * FROM users WHERE name = '" . $name . "'";
$result = $connection->query($query);

// SAFE - parameterized query
$result = $connection->select('users', 'u')
  ->fields('u')
  ->condition('name', $name)
  ->execute();

// SAFE - placeholder
$result = $connection->query(
  'SELECT * FROM {users} WHERE name = :name',
  [':name' => $name]
);

XSS Prevention

Always escape output. Trust the render system:

// VULNERABLE - raw HTML output
return ['#markup' => $user_input];
return ['#markup' => '' . $title . ''];

// SAFE - plain text (auto-escaped)
return ['#plain_text' => $user_input];

// SAFE - use proper render elements
return [
  '#type' => 'html_tag',
  '#tag' => 'div',
  '#value' => $title,  // Escaped automatically
];

// SAFE - Twig auto-escapes
{{ variable }}  // Escaped
{{ variable|raw }}  // DANGEROUS - only for trusted HTML

For admin-only content:

use Drupal\Component\Utility\Xss;

// Filter but allow safe HTML tags
$safe = Xss::filterAdmin($user_html);

Note: Never pass untrusted user input into #markup. Prefer #plain_text, Twig auto-escaping, or safe render elements.

Access Control

Always verify permissions:

// In routing.yml
my_module.admin:
  path: '/admin/my-module'
  requirements:
    _permission: 'administer my_module'  # Required!

// In code
if (!$this->currentUser->hasPermission('administer my_module')) {
  throw new AccessDeniedHttpException();
}

// Entity queries - check access!
$query = $this->entityTypeManager
  ->getStorage('node')
  ->getQuery()
  ->accessCheck(TRUE)  // CRITICAL - never FALSE unless intentional
  ->condition('type', 'article');

CSRF Protection

Forms automatically include CSRF tokens. For custom AJAX:

// Include token in AJAX requests
$build['#attached']['drupalSettings']['myModule']['token'] =
  \Drupal::csrfToken()->get('my_module_action');

Note: Prefer dependency injection over direct \Drupal::service() or \Drupal:: calls in classes.

// Validate in controller
if (!$this->csrfToken->validate($token, 'my_module_action')) {
  throw new AccessDeniedHttpException('Invalid token');
}

File Upload Security

$validators = [
  'file_validate_extensions' => ['pdf doc docx'],  // Whitelist extensions
  'file_validate_size' => [25600000],  // 25MB limit
  'FileSecurity' => [],  // Drupal 10.2+ - blocks dangerous files
];

// NEVER trust file extension alone - check MIME type
$file_mime = $file->getMimeType();
$allowed_mimes = ['application/pdf', 'application/msword'];
if (!in_array($file_mime, $allowed_mimes)) {
  // Reject file
}

Sensitive Data

// NEVER log sensitive data
$this->logger->info('User @user logged in', ['@user' => $username]);
// NOT: $this->logger->info('Login: ' . $username . ':' . $password);

// NEVER expose in error messages
throw new \Exception('Database error');  // Generic
// NOT: throw new \Exception('Query failed: ' . $query);

// Use environment variables for secrets
$api_key = getenv('MY_API_KEY');
// NOT: $api_key = 'hardcoded-secret-key';

Red Flags to Watch For

When you see these patterns, immediately warn:

| Pattern | Risk | Fix | |---------|------|-----| | String concatenation in SQL | SQL injection | Use query builder | | #markup with variables | XSS | Use #plain_text | | accessCheck(FALSE) | Access bypass | Use accessCheck(TRUE) | | Missing _permission in routes | Unauthorized access | Add permission | | Custom controller with no access check | Unauthorized access | Add route permission or access callback | | {{ var\|raw }} in Twig | XSS | Remove \|raw | | Hardcoded passwords/keys | Credential exposure | Use env vars | | eval() or exec() | Code injection | Avoid entirely | | unserialize() on user data | Object injection | Use JSON | | Missing CSRF validation in custom endpoints | CSRF attack | Validate token using csrf_token service | | File upload without validation | Malicious file upload | Validate extension, size, and MIME type | | Direct \Drupal:: usage in classes | Hard to test / bad practice | Use dependency injection | | Logging sensitive data | Information disclosure | Mask or avoid logging sensitive fields |

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: edutrul
• Source: edutrul/drupal-ai
• License: MIT
• Homepage: https://eduardotelaya.com/drupal-ai/

Install and usage instructions live in the source repository linked above.