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Lokesh Kannan
Lokesh Kannan

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OWASP Top 10: A01 & A02 — A Quick Introduction

A01 — Broken Access Control

Broken Access Control occurs when an application fails to properly enforce what users are allowed to access or perform.

For example, if a normal user can access an administrator-only page or view another user's data simply by changing an ID in the URL, the application may have an access control vulnerability.

Common examples include:

Accessing another user's data
Privilege escalation
Accessing admin functions as a normal user
Bypassing authorization checks

Key point: Authentication tells us who you are, while authorization determines what you can do.

A02 — Security Misconfiguration

Security Misconfiguration occurs when an application, server, cloud environment, or other component is configured insecurely.

Common examples include:

Default credentials
Debug mode enabled in production
Unnecessary services or ports exposed
Sensitive files publicly accessible
Missing security headers
Excessive permissions

Even a well-developed application can become vulnerable because of insecure configuration.

Key point: A secure application also needs a securely configured environment.

A01 vs A02

A simple way to remember the difference:

A01 → Permission problem
Who is allowed to do what?

A02 → Configuration problem
Is the system configured securely?

Understanding these two categories is a good starting point for anyone learning web application security and penetration testing.

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