
About
Provide systematic methodologies for identifying and exploiting Insecure Direct Object Reference (IDOR) vulnerabilities in web applications.
name: idor-testing description: "Provide systematic methodologies for identifying and exploiting Insecure Direct Object Reference (IDOR) vulnerabilities in web applications." risk: offensive source: community author: zebbern date_added: "2026-02-27"
AUTHORIZED USE ONLY: Use this skill only for authorized security assessments, defensive validation, or controlled educational environments.
IDOR Vulnerability Testing
Purpose
Provide systematic methodologies for identifying and exploiting Insecure Direct Object Reference (IDOR) vulnerabilities in web applications. This skill covers both database object references and static file references, detection techniques using parameter manipulation and enumeration, exploitation via Burp Suite, and remediation strategies for securing applications against unauthorized access.
Inputs / Prerequisites
- Target Web Application: URL of application with user-specific resources
- Multiple User Accounts: At least two test accounts to verify cross-user access
- Burp Suite or Proxy Tool: Intercepting proxy for request manipulation
- Authorization: Written permission for security testing
- Understanding of Application Flow: Knowledge of how objects are referenced (IDs, filenames)
Outputs / Deliverables
- IDOR Vulnerability Report: Documentation of discovered access control bypasses
- Proof of Concept: Evidence of unauthorized data access across user contexts
- Affected Endpoints: List of vulnerable API endpoints and parameters
- Impact Assessment: Classification of data exposure severity
- Remediation Recommendations: Specific fixes for identified vulnerabilities
Core Workflow
1. Understand IDOR Vulnerability Types
Direct Reference to Database Objects
Occurs when applications reference database records via user-controllable parameters:
# Original URL (authenticated as User A)
example.com/user/profile?id=2023
# Manipulation attempt (accessing User B's data)
example.com/user/profile?id=2022
Direct Reference to Static Files
Occurs when applications expose file paths or names that can be enumerated:
# Original URL (User A's receipt)
example.com/static/receipt/205.pdf
# Manipulation attempt (User B's receipt)
example.com/static/receipt/200.pdf
2. Reconnaissance and Setup
Create Multiple Test Accounts
Account 1: "attacker" - Primary testing account
Account 2: "victim" - Account whose data we attempt to access
Identify Object References
Capture and analyze requests containing:
- Numeric IDs in URLs:
/api/user/123 - Numeric IDs in parameters:
?id=123&action=view - Numeric IDs in request body:
{"userId": 123} - File paths:
/download/receipt_123.pdf - GUIDs/UUIDs:
/profile/a1b2c3d4-e5f6-...
Map User IDs
# Access user ID endpoint (if available)
GET /api/user-id/
# Note ID patterns:
# - Sequential integers (1, 2, 3...)
# - Auto-incremented values
# - Predictable patterns
3. Detection Techniques
URL Parameter Manipulation
# Step 1: Capture original authenticated request
GET /api/user/profile?id=1001 HTTP/1.1
Cookie: session=attacker_session
# Step 2: Modify ID to target another user
GET /api/user/profile?id=1000 HTTP/1.1
Cookie: session=attacker_session
# Vulnerable if: Returns victim's data with attacker's session
Request Body Manipulation
# Original POST request
POST /api/address/update HTTP/1.1
Content-Type: application/json
Cookie: session=attacker_session
{"id": 5, "userId": 1001, "address": "123 Attacker St"}
# Modified request targeting victim
{"id": 5, "userId": 1000, "address": "123 Attacker St"}
HTTP Method Switching
# Original GET request may be protected
GET /api/admin/users/1000 → 403 Forbidden
# Try alternative methods
POST /api/admin/users/1000 → 200 OK (Vulnerable!)
PUT /api/admin/users/1000 → 200 OK (Vulnerable!)
4. Exploitation with Burp Suite
Manual Exploitation
1. Configure browser proxy through Burp Suite
2. Login as "attacker" user
3. Navigate to profile/data page
4. Enable Intercept in Proxy tab
5. Capture request with user ID
6. Modify ID to victim's ID
7. Forward request
8. Observe response for victim's data
Automated Enumeration with Intruder
1. Send request to Intruder (Ctrl+I)
2. Clear all payload positions
3. Select ID parameter as payload position
4. Configure attack type: Sniper
5. Payload settings:
- Type: Numbers
- Range: 1 to 10000
- Step: 1
6. Start attack
7. Analyze responses for 200 status codes
Battering Ram Attack for Multiple Positions
# When same ID appears in multiple locations
PUT /api/addresses/§5§/update HTTP/1.1
{"id": §5§, "userId": 3}
Attack Type: Battering Ram
Payload: Numbers 1-1000
5. Common IDOR Locations
API Endpoints
/api/user/{id}
/api/profile/{id}
/api/order/{id}
/api/invoice/{id}
/api/document/{id}
/api/message/{id}
/api/address/{id}/update
/api/address/{id}/dele
