Understanding and Testing for API1:2023 — Broken Object Level Authorization

Introduction

In the modern digital landscape, APIs (Application Programming Interfaces) have become the backbone of web and mobile applications. They enable seamless communication between different software components and services. However, with the rise of API usage, security vulnerabilities have also increased. One of the most critical vulnerabilities identified in the OWASP API Security Top 10 for 2023 is API1:2023 — Broken Object Level Authorization.

This article provides a technical deep dive into what Broken Object Level Authorization is, how to test for it, and how to integrate its detection into your bug bounty methodology.

What is Broken Object Level Authorization?

Broken Object Level Authorization (BOLA) occurs when an API endpoint exposes direct access to objects based on user-supplied input (like an object identifier), without proper authorization checks. This vulnerability allows an attacker to access, modify, or delete data that they should not have access to.

Key Characteristics:

• Direct Object References: APIs that use object IDs provided by the client (e.g., /api/user/123) without sufficient validation.
• Lack of Authorization Checks: Missing or inadequate checks to verify whether the authenticated user has permission to access the requested object.