IDOR: The Silent Gateway to Data Breaches 

Insecure Direct Object References (IDOR) is an access control vulnerability in web applications. Here, the app fails to confirm if a user is authorized to access a resource or not. It accepts user input to retrieve internal objects without validation. Attackers exploit this weakness by altering URLs, form fields, or other user inputs to gain unauthorized access.

Much like SQL injection or command injection, IDOR poses significant risks to system security. Once exploited, attackers can easily manipulate, steal, or erase sensitive data, undermining confidentiality, integrity, and availability. Safeguarding against IDOR is essential for maintaining robust cybersecurity defenses.  Identifying and addressing these flaws is a priority in Vulnerability Assessment and Penetration Testing (VAPT) or bug bounty programs.

In this blog, we share our experience of identifying an IDOR vulnerability during a real-world security assessment. Further, we provide valuable insights into detecting and mitigating such vulnerabilities effectively.  

Let's dive into the details and address key questions: 

• What is IDOR?  

• How does it work?  

• What are its common types?  

• How can we safeguard against it? And, most importantly, 

• How did we discover an IDOR vulnerability? 

What exactly is an IDOR? 

Insecure Direct Object Reference (IDOR) is a type of access control vulnerability in web applications that exposes sensitive data by allowing unauthorized users to manipulate URLs or form parameters. This occurs when inputs directly access objects like files, directories, or database entries without proper authorization. 

For instance, if a URL like /user/123 displays account details, an attacker could modify it to /user/456 and gain access to another user's data if the system lacks adequate permission checks. 

Recent statistics highlight the ongoing risks of IDOR vulnerabilities. A notable real-world example of this issue arose when a simple Google search for "index of Aadhaar card" revealed websites hosting citizens' Aadhaar card details. This allows individuals to click on those links and potentially access complete information related to others' Aadhaar cards. 

A critical IDOR vulnerability chain in ZITADEL's administration interface (CVE-2025-27507) was rated 9.0/10 on the CVSS scale. Another IDOR issue in RAGFlow allowed unauthorized cross-tenant access, with a CVSS score of 8.1.  

These cases emphasize the importance of continuous testing and robust access controls to mitigate IDOR risks. Ultimately, IDOR is a significant cybersecurity vulnerability, leading to privilege escalation and data breaches.  

How does an IDOR Vulnerability work? 

Let’s take a real-world example how IDOR works-  

Imagine you’re on an e-commerce website, and you’ve just completed a purchase. After successfully making the payment, you land on a confirmation page where all your details are displayed—your name, mobile number, payment card details, home address, and other personal details like email, shipping information, and billing address.  

Now, in the backend, you captured the request in Burp Suite and you found your order id also. Let’s say your order ID value is “C23A10.” You can then modify this ID to “C23DA11” and send the request.  

To your surprise, you can now see the details of someone else’s order, including their personal information. In general, the application only checks if you are authenticated but does not check if the ID is from the same session.  

 This is a clear case of IDOR (Insecure Direct Object References), where the system fails to validate if you're authorized to view another user's data, and you can easily exploit this by manipulating the ID.  

Common Types of IDORs:

Identifiers are increasingly found in HTTP headers or API requests, instead of the user's address bar. Developers must analyze requests to identify and secure IDOR vulnerabilities effectively.  It’s crucial to be vigilant and secure those entry points to protect applications from potential exploitation.   

Here’s a brief overview of a few vulnerabilities.  

URL Tampering 

URL tampering is a simple yet effective IDOR attack where an attacker modifies URL parameters to access unauthorized data.  

Example: Changing values like user_id=123 to user_id=124 in a GET or POST request. This could potentially lead to access another user’s information.  

Vulnerability: The application does not validate the user’s authorization leading to data exposure or privilege escalation.  

Account Takeover 

Account takeover through IDOR occurs when an attacker manipulates user identifiers, such as usernames or email addresses, to gain control over another user's account. Weak access controls allow unauthorized users to perform actions on behalf of others, such as changing account details or resetting passwords.  

Example: If an attacker intercepts a request containing email=target@example.com and replace it with email=attacker@example.com. If the system lacks proper authorization checks, it might send a password reset link to the attacker's email, enabling full account takeover.  

Vulnerability: The application processes email update requests without verifying ownership.  

Unauthorized file access / Path Transversal 

Path traversal, also known as directory traversal, is an IDOR-related vulnerability that allows attackers to manipulate file paths and access restricted directories on a server. By altering parameters referencing files or directories, an attacker can bypass security controls and retrieve sensitive data.  

For example: If a web application fetches user files using a parameter like file=profile.jpg, an attacker could modify it to file=.../.../etc/passwd to access system files.  

Vulnerability: The application doesn't properly validate user-provided file paths. This leads to data leaks, unauthorized modifications, or even remote code execution, posing severe security risks.  

Cookie or JSON ID manipulation

Cookies and JSON objects are essential for managing user sessions and exchanging data between clients and servers. However, when applications fail to enforce strict validation on these stored values, it can be tampered to gain unauthorized access, impersonate users, or alter application behavior.  

Example: An attacker might modify a session cookie containing user_id=1023 to user_id=1024, potentially gaining access to another user’s account. Similarly, if a JSON object holds role-based permissions, altering role=user to role=admin could grant elevated privileges, allowing unauthorized actions within the application.  

Vulnerability: The application fails to validate the authenticity of the session ID or other identifiers used for access control. 

Body Manipulation 

Body manipulation differs from URL ID tampering and JSON/cookie manipulation because it targets the request payload instead of query parameters or stored session data. Unlike URL tampering, which modifies values in the address bar, body manipulation is less visible and commonly affects API-driven applications.  

Example: This attack is often seen in POST, PUT, or PATCH requests, where data is sent within the request body. Changing {"user_id": "1023"} to {“user_id": "1024"} in a request payload leads to unauthorized access grants.  

Vulnerability: The application doesn't properly validate the object reference provided in the request body. 

How to find an IDOR vulnerability?  

During a routine security assessment, we came across an endpoint that handled user-specific data. While analysing its behaviour, we noticed a parameter that seemed to influence data retrieval. What followed was a series of targeted manipulations that ultimately confirmed the presence of an Insecure Direct Object Reference (IDOR) vulnerability. Here’s a breakdown of how we uncovered it.  

Capturing Requests and Identifying the Parameter: 

• After logging into the target website using my first account, we intercepted all network requests using Burp Suite.  

• We identified a request containing a parameter (q) that seemed to be linked to the account information.  

Analysing the Parameter: 

• Initially, we attempted to manipulate the UUID value within the request, but the system rejected it.  

Modifying the Request:

• Instead of using the UUID, we removed everything after ‘?’ in the request URL and replaced it with q=<my_email_id>.  

• The server successfully returned the account details, confirming that the q parameter-controlled access to user data.  

Testing for IDOR: 

• To investigate the possibility of vulnerability, we replaced the email ID with the email of another account that we controlled.  

• The system granted access to the other account’s data, proving the presence of an IDOR flaw.  

Essential Strategies to Prevent Unauthorized Access 

1. Use Indirect Object References 

Avoid exposing direct references (e.g., database IDs) in URLs or API calls. Instead, use secure mappings like hashed tokens or session-based identifiers to prevent attackers from guessing or modifying object references.  

2. Validate User Permissions on Every Request 

Even after authentication, ensure that each action or request is verified for proper authorization. Attackers should never be able to manipulate object references to access data they don’t own.  

3. Implement Rate Limiting and Monitoring

Attackers often enumerate object references by making multiple requests with different parameter values. Implementing rate limiting can help detect and block such attempts by restricting the number of requests from a single IP within a time frame. Additionally, monitoring logs for unusual access patterns can help identify and mitigate potential IDOR exploits before they escalate.  

4. Enforce Strict Access Controls

Implement role-based and permission-based access control mechanisms. Ensure access is checked at every request, not just during login, to prevent unauthorized access via manipulated references.  

5. Regular Security Reviews and Code Audits

Consistently reviewing application code and security configurations helps identify and address IDOR vulnerabilities before they can be exploited. Conducting structured security audits ensures that access control mechanisms are correctly implemented and enforced. This includes analysing API endpoints, database queries, and session handling to prevent unintended data exposure. Additionally, maintaining proper documentation of security policies and best practices helps teams stay aligned with secure coding standards.  

6. Use Secure Development Frameworks
Modern frameworks like Django, Ruby on Rails, and Spring offer built-in security tools to prevent IDOR vulnerabilities. Features like ORM abstraction and robust authorization checks help enforce access control and validation. Follow their best practices to avoid risky custom code. This strengthens your app’s defences efficiently.  

7. Implement Fuzz Testing for IDOR Detection

Perform fuzz testing with unexpected inputs to identify IDOR vulnerabilities before deployment. Test various edge cases to ensure the application handles manipulated requests securely. Proper validation and error handling can prevent unauthorized access attempts.  

Final Thoughts

IDOR vulnerabilities pose a significant risk to data security, often slipping past automated security tools due to the need for context-aware access validation. While implementing strong authorization checks, indirect object references, and secure development practices can minimize risks, continuous vigilance is key.  

Regular assessments, strict access control enforcement, and secure coding habits should be an ongoing priority for developers and organizations alike. By proactively addressing IDOR risks, businesses can strengthen their security posture and safeguard user trust in an increasingly interconnected digital world.  

Recommendations

• Review code and application endpoints for IDOR vulnerabilities 

• Replace direct database identifiers in URLs or API parameters with indirect ones. 

• Ensure all requests to sensitive resources have proper authorization checks. 

• Use fuzz testing during development to find IDOR risks through manipulated inputs. 

• Apply rate limiting and monitoring to catch suspicious activity. 

• Train developers on IDOR risks and prevention practices. 

• Follow security standards like ISO 27001, PCI-DSS, GDPR, and other relevant frameworks.  

AuthenticOne provides VAPT services to detect and fix weaknesses in your IT systems. By combining Vulnerability Assessments with Penetration Testing, AuthenticOne identifies risks and shows how they could be exploited in real-world scenarios, ensuring a stronger defense against cyber threats.  

Reach out to us today to find out more about VAPT services.