Preventing Access Control Vulnerabilities

Effective access control starts with the principle of "deny by default"—unless explicitly granted permission, users should have no access. This reverses the common but dangerous pattern of granting broad access and then trying to restrict it. Implement access control checks on the server side for every sensitive operation, never trusting client-side restrictions alone.

Use frameworks and libraries that provide robust access control mechanisms rather than building your own. Modern frameworks offer role-based access control (RBAC) or attribute-based access control (ABAC) systems that have been tested and hardened over years of use. Always validate that the current user has permission to access the specific resource they're requesting, not just that they're logged in. Log access control failures and monitor for patterns that might indicate attack attempts. Remember, access control isn't a feature you add—it's a fundamental requirement that must be designed into your application from the beginning.