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Introduction
Insecure Direct Object Reference (IDOR) vulnerabilities remain a critical threat to web applications, allowing attackers to manipulate references and access unauthorized data. A recent real-world example demonstrates how a simple parameter tampering trick bypassed security checks—deleting a project by altering `projectid=10678` to projectid[]=10678.
Learning Objectives
- Understand how IDOR vulnerabilities bypass authorization checks.
- Learn how to test and exploit IDOR flaws in APIs.
- Apply mitigation techniques to secure your applications.
1. What Is an IDOR Vulnerability?
An Insecure Direct Object Reference (IDOR) occurs when an application exposes internal object references (like IDs, filenames, or keys) without proper authorization checks. Attackers manipulate these references to access unauthorized data.
Example Exploit
Original Request:
DELETE /api/projects?projectid=10678
Response: `400 Bad Request (Invalid projectid)`
Modified Request (Exploit):
DELETE /api/projects?projectid[]=10678
Response: `200 OK (Project deleted)`
Why This Works
- The backend may mishandle array inputs (
projectid[]), bypassing validation. - Improper input sanitization leads to unexpected behavior.
2. How to Test for IDOR Vulnerabilities
Manual Testing with cURL
Check for IDOR by modifying parameters:
curl -X DELETE "http://example.com/api/projects?projectid=10678" curl -X DELETE "http://example.com/api/projects?projectid[]=10678"
Automated Testing with Burp Suite
1. Intercept a request in Burp.
2. Use Burp Repeater to modify parameters.
3. Test different payloads (`projectid=1`, `projectid[]=1`, `projectid=../otheruser`).
3. Exploiting IDOR in Different Scenarios
Bypassing Numeric ID Checks
If an API expects a number but processes an array:
GET /api/user?uid=1001 → 403 Forbidden GET /api/user?uid[]=1001 → 200 OK (Data leaked)
Path Traversal + IDOR
Combine IDOR with directory traversal:
GET /download?file=../otheruser/report.pdf
4. Mitigation Strategies
Implement Proper Access Controls
- Use role-based access control (RBAC).
- Validate user permissions before processing requests.
Use Indirect References (UUIDs, Tokens)
Instead of numeric IDs, use unpredictable references:
DELETE /api/projects?token=abcd1234-5678-efgh-9101
Input Validation & Sanitization
- Reject unexpected input types (e.g., arrays when expecting integers).
- Use strict parameter parsing.
- Advanced Exploitation: Mass Assignment & Batch Deletion
Mass Assignment Attack
If an API accepts arrays for batch operations:
POST /api/projects/delete
{"projectids": [10678, 10679, 10680]}
Mitigation: Limit batch operations to admin roles only.
What Undercode Say
- Key Takeaway 1: IDOR flaws often arise from weak input validation and poor authorization checks.
- Key Takeaway 2: Simple parameter tampering (e.g., adding
[]) can bypass security controls.
Analysis:
This exploit highlights how minor oversights in API design can lead to major breaches. Developers must enforce strict input validation and implement proper access controls. Automated scanners often miss such logic flaws, making manual testing essential.
Prediction
As APIs become more complex, IDOR attacks will evolve—especially in microservices architectures. Future exploits may leverage GraphQL queries or JWT tampering. Proactive security testing and zero-trust principles will be critical in mitigating these risks.
For the full writeup, visit: https://lnkd.in/gHdnCnkn
IT/Security Reporter URL:
Reported By: Bipin Rai – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
