IDOR Vulnerability: Understanding and Exploiting Insecure Direct Object References

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

You Should Know:

1. Identifying IDOR Vulnerabilities

  • Check if object references (e.g., user_id=123, file=report.pdf) are predictable.
  • Test parameter tampering in URLs, APIs, or hidden form fields.

2. Exploiting IDOR (Example Scenarios)

  • URL Tampering:
    curl -X GET "https://example.com/profile?user_id=1001"

Change `user_id` to access other accounts.

  • API Manipulation:
    curl -X GET "https://api.example.com/invoices/500" -H "Authorization: Bearer TOKEN"

Replace `500` with another invoice ID.

3. Mitigation Techniques

  • Access Control Checks:
    Django Example 
@login_required 
def view_profile(request, user_id): 
if request.user.id != user_id: 
raise PermissionDenied

  • Use Indirect References (UUIDs instead of sequential IDs):

    CREATE TABLE users (id UUID PRIMARY KEY, username VARCHAR(50));

  • Rate Limiting & Logging Suspicious Activity:

    Fail2Ban rule for excessive IDOR attempts 
failregex = ^<HOST>.(user_id=|invoice=).(403|404)

4. Automated Testing with Burp Suite

  • Use Burp Intruder to brute-force object references.
  • Configure payloads for sequential or predictable IDs.

5. Practice Lab (TryHackMe/HTB)

What Undercode Say:

IDOR remains a critical flaw due to poor access control design. Always implement:
– Role-Based Access Control (RBAC)
– Randomized Tokens (JWT/OAuth)
– Audit Logs for Unauthorized Access

Expected Output:

A secure web app that prevents unauthorized data access via proper reference validation.

Prediction:

As APIs grow, IDOR attacks will shift towards misconfigured GraphQL and REST endpoints, requiring stricter API gateways.

Note: No direct cyber course URLs found, but ethical hacking platforms like TryHackMe cover IDOR extensively.

IT/Security Reporter URL:

Reported By: Activity 7336534340719300609 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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