How to Exploit IDOR Vulnerabilities for Bug Bounty Success

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Insecure Direct Object Reference (IDOR) is a common web vulnerability that occurs when an application exposes internal objects (e.g., files, database entries) without proper authorization checks. Attackers manipulate object references (e.g., user IDs, document IDs) to access unauthorized data.

You Should Know:

1. Identifying IDOR Vulnerabilities

  • Manual Testing:
  • Change parameter values in URLs (e.g., `/user?id=123` → /user?id=124).
  • Modify API request bodies (e.g., `{“user_id”: 100}` → {"user_id": 101}).
  • Test UUIDs, numeric IDs, and hashed references.

  • Automated Tools:

  • Burp Suite (Intruder, Repeater)
  • OWASP ZAP (Forced Browse)
  • Param Miner (Burp Extension)

2. Exploiting IDOR in Different Scenarios

A. URL Parameter Tampering

curl -X GET "https://example.com/api/user?id=100" -H "Authorization: Bearer token123"

Change `id=100` to `id=101` to test access control.

B. API Request Manipulation

curl -X POST "https://example.com/update_profile" -H "Content-Type: application/json" -d '{"user_id": 100, "name": "attacker"}'

Modify `user_id` to escalate privileges.

C. File/Document Access

wget https://example.com/download?file=invoice_100.pdf

Try `file=invoice_101.pdf` to check for unauthorized access.

3. Bypassing Defenses

  • Use Encoded IDs: 
    echo "100" | base64  MTAw
curl "https://example.com/user?id=MTAw"
  • Test UUID Variations: 
    Replace UUIDs in requests
curl "https://example.com/data?uuid=6ba7b810-9dad-11d1-80b4-00c04fd430c8"
  • HTTP Method Switching:
    Change `GET` to `POST` or `PUT` to bypass weak checks.

4. Reporting IDOR for Bug Bounty

  • Proof of Concept (PoC):
  • Show unauthorized access to another user’s data.
  • Include screenshots and HTTP requests.
  • Impact:
  • Data leakage, account takeover, or privilege escalation.

What Undercode Say

IDOR remains a critical bug in web apps due to poor access control. Always test:
– Horizontal Privilege Escalation (accessing another user’s data).
– Vertical Privilege Escalation (accessing admin functions).
Use Burp Suite and custom scripts to automate testing.

Prediction

As APIs grow, IDOR attacks will increase. Companies must enforce role-based access control (RBAC) and object-level permissions.

Expected Output:

  • Unauthorized data access via IDOR.
  • Bug bounty submission with PoC.
  • Mitigation: Implement proper authorization checks.

Relevant URLs:

References:

Reported By: Amit Khandebharad – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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