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Glib Rulev
Glib Rulev

OWASP TOP 1: Broken Access Control

Despite being a fundamental security principle, access control failures are still among the most common — and most dangerous — vulnerabilities in modern applications.

🔍 What is Broken Access Control?

It occurs when users are able to act outside their intended permissions. This can lead to unauthorized information disclosure, data modification, or even complete system compromise.

🧪 Example

Imagine an application where user profiles are accessed via predictable URLs like: /users/profile/123

If there’s no proper access control check in place, a malicious user could simply change the ID and access someone else’s data. For example: /users/profile/124 = Data breach in one click.

📊 Statistics

Recent studies show that over 90% of applications were tested for some form of broken access control — and many failed.

✅ Best Practices to Prevent This

  1. Deny by Default
    Only allow access when explicitly granted. If access rules aren’t clearly defined for a resource, no one should be able to reach it — not even authenticated users.

  2. Enforce Access on the Server Side
    Never rely on the user interface to control access. Hiding buttons or menu items in the frontend is not security. Always verify permissions on the backend, where enforcement can’t be bypassed.

  3. Implement Role-Based Access Control (RBAC)
    Use structured roles (e.g., user, manager, admin) to control who can access what. Keep it simple and consistent — and regularly review roles to avoid privilege creep.

  4. Avoid Predictable Identifiers in URLs
    Using sequential or guessable IDs (like /user/101, /user/102) makes enumeration easy for attackers. Use UUIDs or indirect references, and always validate ownership on the server.

  5. Log and Monitor Access Violations
    Record any failed or unauthorized access attempts — they’re often the first sign of probing or a misconfigured permission. Set up alerts for repeated or high-risk violations.

🔐 Final Thoughts

Security isn’t just about firewalls and encryption — it’s about ensuring every user sees only what they’re supposed to. Let’s build with access control in mind from day one.