How to Find IDOR Vulnerabilities: The Bug Bounty Hunter's Practical Guide

How to Find IDOR Vulnerabilities: The Bug Bounty Hunter's Practical Guide Insecure Direct Object References (IDOR) are consistently one of the highest-paid vulnerability classes in bug bounty programs. They're conceptually simple, devastatingly impactful, and — if you know where to look — surprisingly common even in mature applications. This is the guide I wish I'd had when I started. What Is IDOR, Actually? IDOR happens when an application uses user-controllable input to access objects directly — without verifying the user has permission to access that specific object. The classic example: GET /api/users/12345/orders Authorization: Bearer your_token_here What happens if you change 12345 to 12346 ? If the server returns another user's orders — that's IDOR. But modern IDOR is more nuanced than just incrementing numbers. Let's go deeper. The IDOR Attack Surface Map Before you start testing, build a mental map of where objects live in the application: 1. URL Path Parameters /api/invoices/