What are common pitfalls when developing a CMS that allows users to create and integrate their own modules using PHP?

One common pitfall when developing a CMS that allows users to create and integrate their own modules using PHP is the lack of proper input validation, which can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To solve this issue, always sanitize and validate user input before executing any database queries or rendering output to prevent malicious code injection.

// Example of sanitizing user input using PHP filter functions
$user_input = $_POST['user_input'];
$sanitized_input = filter_var($user_input, FILTER_SANITIZE_STRING);