How to Protect APIs from Insecure Direct Object References (IDOR)

How to Protect APIs from Insecure Direct Object References (IDOR)

APIs have become the cornerstone of contemporary software, facilitating dynamic interactions and seamless data exchanges. While developers harness APIs to craft enriched user experiences, it’s imperative that these interfaces are not only efficient but also secured against vulnerabilities. One such subtle yet pervasive vulnerability is IDOR, or Insecure Direct Object References. This vulnerability poses a significant threat, potentially granting unauthorized data access and jeopardizing both businesses and their users.

Read on to find out more on how to protect APIs from IDOR.

What Is An Insecure Direct Object Reference(IDOR)?

Insecure Direct Object References occur when an API endpoint exposes a reference to an internal implementation object. Attackers can manipulate these references to gain unauthorized access to data.

Examples of IDOR

The following examples can be applied to similar situations.

User Profile Access

An API endpoint is designed to fetch user profiles and if proper checks aren’t in place, an attacker could modify the userId parameter to view profiles of other users.

GET /api/users/{userId}

Order Details Access

Consider an e-commerce platform where users can view their order details where an attacker could iterate through different orderId values to fetch details of orders placed by other users.

GET /api/orders/{orderId}

File Retrieval

If an application allows users to upload and retrieve files with an endpoint and without proper authorization checks, an attacker could potentially access files uploaded by other users.

GET /api/files/{fileId}

What is the Impact of an IDOR breach?

Data Breach

The most direct consequence is unauthorized data access. Sensitive user data like personal details, financial information, or business-critical data can be exposed.

Data Manipulation

In some cases, IDOR might not just be used to view data but also to modify it. For instance, changing the parameters in a PUT or POST request can lead to data being altered.

Reputation Damage

Data breaches, especially those involving user data, can severely damage the reputation of a business. It can lead to loss of trust, users, and potential legal consequences.

Financial Loss

Especially in scenarios where financial transactions are involved, IDOR can lead to monetary losses.

How Can You Protect APIs From IDOR?

These few simple steps can help protect against an IDOR attack.

Always Authenticate and Authorize

Ensure that every API request is both authenticated (the user is who they claim to be) and authorized (the user has permission to perform the requested action).

app.get('/api/orders/:orderId', (req, res) => {
let orderId = req.params.orderId;
if (auth.isUserAuthenticated() && auth.isOrderOwnedByUser(orderId)) {
} else {

Avoid Exposing Direct Object References

Instead of using database IDs, consider using UUIDs or other non-sequential identifiers that are harder to guess.

Implement Rate Limiting

This can prevent attackers from easily iterating through different IDs to find valid ones.

Use Proper HTTP Verbs

Ensure that data-changing operations like PUT, POST, or DELETE are protected against unauthorized access.

Logging and Monitoring

Keep detailed logs of API access patterns. Unusual patterns, like rapid sequential ID access, can be flagged for review.

Regular Audits

Periodically review and test your API endpoints for vulnerabilities. Tools like OWASP ZAP can help automate some of these checks.


Developers must ensure APIs are secure and resilient. By preventing IDOR vulnerabilities, we preserve sensitive data and maintain user trust in our apps. In a world of growing data breaches, proactive API security may set a platform apart.

Check your APIs often.

For more insights, tutorials, and a community of security-aware developers, visit BUZZ. Together, we will make security accessible to all!

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