Understanding and Testing for API2:2023 — Broken Authentication

Introduction

APIs (Application Programming Interfaces) are integral to modern applications, facilitating communication between services and enabling rich user experiences. However, they also introduce security challenges. One of the critical vulnerabilities highlighted in the OWASP API Security Top 10 for 2023 is API2:2023 — Broken Authentication.

This article provides a comprehensive technical overview of Broken Authentication vulnerabilities in APIs, methods to test for them, and strategies to integrate their detection into your bug bounty methodology.

What is Broken Authentication?

Broken Authentication refers to flaws in an API’s authentication mechanisms that allow attackers to bypass authentication controls and assume the identities of other users. These vulnerabilities arise due to incorrect implementation of authentication functions, enabling attackers to:

• Compromise Authentication Tokens: Steal or manipulate tokens to gain unauthorized access.
• Exploit Implementation Flaws: Leverage weaknesses like improper password handling or insecure session management.
• Assume User Identities: Temporarily or permanently impersonate other users.

Key Characteristics:

• Weak Password Policies: Allowing simple or commonly used passwords.