Critical IDOR in a University System: A Case Study on Ethical Hacking and Student Data Exposure

January 3, 2026 • 5 min read

A real-world IDOR vulnerability in a university API exposed private student data due to missing authorization and sequential IDs. This write-up explains the discovery, impact, root cause, and defensive lessons.

Disclaimer

This article is shared strictly for educational and defensive security awareness purposes.
All domains, endpoints, identifiers, and institutions are redacted or anonymized.
No real student data was extracted, stored, or misused.
Testing was performed only within an authorized context, following responsible disclosure practices.

Introduction

Security vulnerabilities are often associated with large tech companies or high-profile platforms.
However, educational institutions-despite handling vast amounts of sensitive personal data-are frequently overlooked.

In this case, a security researcher discovered a critical Insecure Direct Object Reference (IDOR) vulnerability in a university system that exposed private student information at scale. The flaw was simple, severe, and entirely preventable.

This write-up documents what was found, why it mattered, how it happened, and what lessons developers and institutions must learn.

What Is an IDOR?

An Insecure Direct Object Reference (IDOR) occurs when an application exposes internal object identifiers (such as user IDs or document IDs) and fails to verify whether the requesting user is authorized to access the referenced object.

In plain terms:

If changing a number or identifier in a request gives access to someone else’s data - that’s an IDOR.

IDOR vulnerabilities are a subset of Broken Access Control, one of the most critical and common issues in modern web applications and APIs.

Discovery: From Normal Testing to a Serious Finding

The researcher began by performing routine endpoint testing and fuzzing, analyzing how the university platform handled different API requests. Most endpoints behaved correctly, enforcing authentication or returning access-denied responses.

One endpoint, however, behaved differently.

https://[redacted]/api/student/profile/46500

Unlike other pages that returned styled HTML, this endpoint returned raw JSON data containing a student profile. When accessed with the researcher’s own student ID, it displayed personal information as expected.

Curiosity led to a single test.

The numeric ID in the URL was incremented.

https://[redacted]/api/student/profile/46501

The response returned another student’s complete profile.

No authentication error.
No authorization failure.
No warning.

Just data.

A diagram representing an API response displaying structured JSON output, with sensitive student profile fields like names and IDs highlighted and redacted for privacy.

The Escalation Risk: Sequential Identifiers

The severity of the issue increased dramatically once a pattern became clear:

Student IDs were sequential
No authentication checks were enforced
No authorization logic validated ownership

This meant the entire student database was theoretically enumerable.

A simple loop could retrieve thousands of student records:

import requests

for student_id in range(46500, 48000):
    response = requests.get(
        f"https://[redacted]/api/student/profile/{student_id}"
    )
    if response.status_code == 200:
        print(f"Student {student_id}: {response.json()}")

Although this script was never executed beyond proof-of-concept, its existence highlights how trivial exploitation would be for a malicious actor.

A minimal educational cybersecurity diagram in a dark theme, illustrating how incrementing sequential numeric identifiers in API requests leads to accessing different user records.

Data at Risk

The exposed JSON responses contained highly sensitive information, including:

Full names
University email addresses
Contact information
Course enrollments
Academic records
Student identification numbers
Historical academic data

This is not just personal data - it is regulated, protected information.

Impact Assessment

A conceptual illustration using icons to represent the severe impact of a university data breach, highlighting privacy violations, legal liabilities, and large-scale student data exposure.

This vulnerability represented a catastrophic security failure.

Technical Impact

Complete lack of access control
Unauthenticated API data exposure
Trivial mass enumeration

Privacy Impact

Exposure of personally identifiable information (PII)
Violation of student confidentiality
Potential identity theft risks

Legal & Compliance Impact

Serious GDPR violations
Breach of educational data protection laws
Institutional liability

Reputational Impact

Loss of trust from students and faculty
Long-term damage to institutional credibility

Root Cause Analysis

A technical flow diagram illustrating the vulnerability's root cause: a client request reaches the API endpoint, bypasses a missing authentication check, and results in unauthorized data being returned.

The vulnerability existed due to a combination of fundamental security failures:

No Authentication Enforcement
The API endpoint was accessible without verifying user identity.
No Authorization Checks
The backend did not verify whether the requester was allowed to access the specified student record.
Sequential Object Identifiers
Predictable IDs made enumeration trivial.
Lack of Rate Limiting
No safeguards existed to detect or block automated access.
Environment Misconfiguration
Development-style endpoints were exposed in a production environment.

This was not a single mistake-it was a chain of missing controls.

Responsible Disclosure and Ethical Conduct

A symbolic illustration showing the ethical Responsible Disclosure process flow: a security researcher identifies an issue, privately reports it to the organization, leading to a remediation fix.

The researcher followed ethical security practices throughout the process:

Testing stopped immediately after confirming the vulnerability
No large-scale data extraction was performed
No third-party data was stored or shared
A detailed responsible disclosure report was prepared
Remediation guidance was included for the institution

This approach ensured student safety while still enabling the institution to fix a critical flaw.

How This Should Have Been Prevented

A defensive architecture diagram mapping recommended security controls, showing layers for strong authentication, strict authorization checks, rate limiting, and the use of non-sequential UUIDs.