The Ultimate Guide to Finding IDOR Vulnerabilities — Guaranteed Approach + Top Payloads & Tools

IDOR (Insecure Direct Object Reference) is one of the most powerful, common, and easy-to-find web vulnerabilities that allow attackers to access data they shouldn’t — just by tweaking an identifier in the request.

Imagine accessing someone else’s invoice, account, message, or file simply by changing a user ID, file name, or object number in the URL or request body.

This vulnerability is listed under Broken Access Control in the OWASP Top 10.

🧨 Real-World Impact of IDOR

• ✅ Accessing another user’s private data (e.g., orders, invoices, chats)
• ✅ Downloading someone else’s documents
• ✅ Modifying other users’ settings, roles, or even deleting their accounts
• ✅ Accessing paid/premium features without authorization

🚀 The Guaranty Way to Find IDOR Vulnerabilities

Finding IDOR is not about throwing thousands of payloads blindly. It’s about knowing where to look, how to interact with the application, and what tools to leverage.

Let’s go step by step:

✅ Step 1: Understand the App Logic and User Roles

Start by mapping:

• 👤 All user roles: guest, regular user, premium user, admin, etc.
• 🔀 All actions: view, edit, delete, download, etc.
• 📦 All objects: user IDs, order IDs, invoice numbers, document hashes, file names

✅ Step 2: Interact as Multiple Users

Create:

• Two accounts (or more)
  • UserA: the attacker
  • UserB: the victim

Log in with both and compare their:

• Endpoints
• Request/response patterns
• Object IDs and access tokens

Use two browsers, two incognito sessions, or tools like Multilogin, Firefox Containers, or Postman environments.

✅ Step 3: Identify Object References

Look for predictable identifiers in:

• 🔗 URLs
  • /profile/1234
  • /api/user?id=5678
  • /orders/9b8a-f3b1a-77cd
• 📩 POST/PUT/DELETE bodies
  • {"user_id":1234}
  • {"document":"invoice_003.pdf"}
• 📂 File names, paths, and query params
  • download.php?file=report1.pdf

If you see sequential IDs or UUIDs, that’s a green flag.

✅ Step 4: Swap IDs and Analyze the Response

Now try replacing your user ID with another one:

• 1234 ➡️ 1235
• order_id=1001 ➡️ order_id=1002
• GET /files/invoice.pdf ➡️ invoice2.pdf

Analyze:

• 📩 HTTP status code: 200 vs 403 vs 404
• 🔍 Response body: Do you get someone else’s data?
• 🧱 API errors: Sometimes an error gives away clues

✅ Step 5: Bypass Checks (Token, Headers, Role)

Some apps may use Access Control checks based on:

• JWT tokens
• Cookies
• Custom headers (X-User-ID, X-Auth)

Try:

• Replaying the request without tokens
• Using another user’s token
• Adding/removing headers

✅ Step 6: Try These IDOR Payloads

Here are top payload variations to help you test IDOR systematically:

🎯 Top IDOR Payloads & Variations

GET /api/user/1234             ➡️ Change to 1235
GET /api/user?id=1234          ➡️ Change to ?id=1235
GET /files/invoice-1234.pdf    ➡️ invoice-1235.pdf
POST /profile/update
Body: {"user_id":1234}         ➡️ Change to 1235

PUT /api/order/1001/ship       ➡️ 1002
DELETE /account?id=987         ➡️ Another user’s ID
GET /chat/message/abcd1234     ➡️ Change to abcd1235

💡 Bonus Trick: Sometimes UUIDs look random but are actually guessable. Try:

• Incrementing the last digit
• Bruteforcing the UUID using a wordlist
• Observing patterns across multiple accounts

🛠️ Tools to Use for Hunting IDOR

Here are the top tools that make IDOR hunting easier and faster:

🔧 Manual Testing Tools

ToolPurpose

Burp Suite (with extensions)Intercept, modify, replay requests

PostmanReplaying API calls manually

AuthMatrix (Burp extension)Multi-user access control testing

Autorize (Burp extension)Automated IDOR detection

HackBar (browser extension)Quick parameter modification

FoxyProxy + Cookie editorsManage multiple users

🧠 Automation & Enumeration

ToolPurpose

ffufBruteforce object IDs or file names

Intruder (Burp)Parameter fuzzing and bruteforce

Param Miner (Burp)Discover hidden/unused parameters

DalFoxPrimarily XSS but detects some IDOR cases

ArjunDiscovering hidden parameters

🕵️‍♂️ Example Workflow: Manual + Automated

1. Register UserA and UserB
2. Intercept requests from UserA using Burp
3. Use Intruder to modify user_id, order_id, etc.
4. Observe response changes: did UserA access UserB‘s data?
5. Automate with AuthMatrix to test multiple roles simultaneously

🔥 Bonus Pro Tips

• Don’t ignore 403s or 401s — apps may leak error messages that help identify protected objects.
• Always test with multiple users — especially for things like roles, premium vs free, admin vs staff.
• Chain IDOR with other bugs — like SSRF, file download, or RCE for serious impact.
• Test on mobile APIs too — mobile apps often have weaker access control than web apps.

🧱 How to Prevent IDOR Vulnerabilities

For devs and defenders:

• Never trust client-side identifiers
• Always perform server-side authorization checks
• Use proper session-based or RBAC-based access control
• Avoid exposing object references directly — use indirect references or opaque IDs
• Implement rate limiting, logging, and monitoring

📚 Real-World IDOR Exploits

• Facebook Bug Bounty: Download any user’s private videos via IDOR
• Uber: Access and modify trip details of other riders
• Instagram: Delete any photo using media ID

You can find more at HackerOne Hacktivity or Bugcrowd Disclosures.

🏁 Conclusion

IDOR is low-hanging fruit with high impact. It doesn’t need elite exploitation skills — just curiosity, observation, and patience.

To recap:

• 🧠 Understand the logic
• 👨‍🔧 Interact as multiple users
• 🔄 Swap object references
• 🧪 Test everything: GET, POST, PUT, DELETE
• 🚀 Use the right tools to automate and scale

If you follow this process consistently, you will find IDOR vulnerabilities — guaranteed.