In modern applications, authentication is usually implemented well. You log in, you get access to your dashboard, and everything seems secure. But security failures rarely happen at the login screen anymore — they happen after login. One of the most common examples of this is IDOR (Insecure Direct Object Reference), and it continues to show up across real-world applications, from startups to enterprise internal tools.

IDOR is an access control vulnerability where an application uses user-supplied input (like IDs in URLs or API parameters) to directly fetch backend data objects — without properly verifying whether the logged-in user is actually authorized to access that specific object.

Instead of validating permissions, the application simply trusts whatever identifier is sent from the client. If attackers can guess or modify those identifiers, they can access data that doesn't belong to them — often without triggering alerts.

This vulnerability is so widespread that it ranks #1 in OWASP Top 10 2025 under Broken Object Level Authorization (BOLA). Realistically, if you test enough real-world applications, you will encounter IDOR. It's especially common in HR portals, fintech dashboards, admin panels, healthcare systems, and legacy enterprise applications.

The Core Problem: Authentication ≠ Authorization

Most vulnerable applications do this:

✔ Check if user is logged in ❌ Fail to check if user is allowed to access a specific record

The system asks: "Are you authenticated?"

But it forgets to ask: "Should you be allowed to access THIS exact resource?"

That gap is where IDOR lives.

Lab Scenario — Advanced IDOR in Practice

For this lab, I started with credentials for a single user:

Username: alice Password: password123

After logging in, I could see Alice's normal employee details:

• Department
• Role
• Salary
• Notes

Everything looked expected. But then I noticed something interesting — the employee profile used a numeric identifier:

view?eid=2001

Seeing direct numeric IDs in URLs is often a red flag. It suggests the backend might be fetching records purely based on that ID — without validating ownership.

Exploitation Phase

Step 1 — ID Manipulation

I changed the value from:

eid=2001 → eid=2002

This immediately exposed another employee's profile:

Bob Smith Department: IT Operations Role: Systems Analyst Salary: $72,000 Notes: Privileged server access

At this point, the risk becomes obvious. I now have visibility into:

• Organizational structure
• Privileged access holders
• Salary data
• Potential high-value targets

Step 2 — Further Enumeration

I changed the value again:

eid=2003

This revealed:

Charlie Adams Department: Human Resources Role: HR Manager Salary: $90,000 Notes: Handles termination records

Now this is clearly horizontal privilege escalation via IDOR combined with sensitive data exposure.

Real-World Impact

IDOR is rarely "just data leakage." It usually cascades into larger risks.

Data Exposure Risks

• Salary information (privacy + compliance violations)
• Role and permission structure
• Internal operational notes
• Infrastructure access hints

Attack Chain Enablement

• Targeted phishing and social engineering
• Insider threat simulation
• Credential stuffing targeting high-privilege users
• Lateral movement mapping

Business Risks

• Regulatory penalties (GDPR, data protection laws)
• Reputation damage
• Legal liability
• Competitive intelligence leakage

Another dangerous aspect: IDOR traffic often looks like normal user activity, making detection difficult.

Root Causes

Why does IDOR keep happening?

• Authorization checked only at login
• Over-reliance on predictable numeric IDs
• API-first development without access policy enforcement
• Frontend assumed to enforce security
• Lack of authorization test coverage

Remediation Strategy

1. Enforce Object-Level Authorization (Mandatory)

Every request must validate:

Does this user have permission to access THIS exact object?

Not just authentication status.

2. Backend Ownership Validation

Secure query pattern example:

SELECT * FROM employees
WHERE employee_id = request_eid
AND owner_user_id = session_user_id

3. Avoid Direct Exposure of Internal IDs

Use:

• Indirect object references
• Tokenized mapping systems
• Access-scoped identifiers

4. Use UUIDs (Defense in Depth)

UUIDs don't fix IDOR alone but reduce easy enumeration attacks.

5. Centralized Authorization Enforcement

Use middleware or policy engines instead of scattered permission checks.

6. Security Testing Integration

Include:

• Authorization unit tests
• ID fuzzing
• BOLA / IDOR automated scanning

Final Takeaway

IDOR is not a "small bug." It's usually a sign that access control architecture is fundamentally broken.

If you find one IDOR, assume more exist until proven otherwise.

In this lab, access to one account exposed multiple employee records — including roles, salaries, and operational notes. In a real production environment, that level of exposure would likely be classified as High to Critical severity.

BY HACKACADEMY — Mentor: Winston Ighodaro Follow me: Shreya