The Silent Vulnerability: Uncovering IDOR in Web Security

Understand This Critical Vulnerability with Basic Knowledge!

Prerequisites

1. Basic Web Application Knowledge

• Understanding how web applications work, including how data is requested and displayed (e.g., through URLs and parameters).

2. Knowledge of HTTP Methods

• Familiarity with HTTP requests (GET, POST) and how parameters are passed in the URL or form data.

What is a IDOR?

IDOR, or Insecure Direct Object References, is a type of security flaw in web applications.

Here’s a simple explanation:

Imagine you’re using an app that gives you access to your personal files or information, like a bank or social media account. Each file or piece of information has a unique ID, like “file123” or “account456.” Normally, you should only be able to see and access your own files.

But with IDOR, there’s a problem: if you change the ID in the web address (URL), you might accidentally (or intentionally) see someone else’s information. For example, if you’re looking at your file and you change the URL from “file123” to “file124,” you could access someone else’s file if the app isn’t properly secured.

This happens because the app doesn’t check if you’re really allowed to see that file. IDOR lets people access things they shouldn’t, which can lead to big privacy and security issues.

In short: IDOR is when a web app doesn’t properly check who’s allowed to access certain files or data, leading to unauthorized access.

Let us see a example shall we😉

Now try to imagine this, Imagine you’re logging into a banking website, and your account is referenced by a unique ID in the URL. It looks something like this:

https://example.com/user.php?account=1009

In this example, the request is asking for information related to account number 1009. Here’s what’s happening behind the scenes: you’re sending a GET request to the server, which includes your account ID (1009), and the server responds with your account details.

Where IDOR Becomes Dangerous

Now, let’s say you’re curious. Instead of sticking with your own account ID, you manually change the URL to:

https://example.com /user.php?account=1010

If the server doesn’t properly check whether you’re allowed to view that account, you might suddenly find yourself looking at someone else’s private information — just by changing a number in the URL! This is the essence of IDOR: a vulnerability that happens when an application doesn’t validate whether users have the proper authorization to access a resource.

How Attackers Exploit This

Attackers can easily abuse IDOR vulnerabilities by systematically altering account numbers or IDs in URLs.

• The attacker manipulates the URL

https://example.com/user.php?account=1009

• They modify the account number to 1010 and send the request again.
• If the server doesn’t enforce proper authorization checks, the attacker receives a response containing another user’s account details.

Preventing IDOR: What Should Developers Do?

To protect against IDOR, developers need to ensure that access controls are enforced properly:

• Authentication: Ensure the user is logged in.
• Authorization: Always verify that the logged-in user has permission to access the requested resource.
• Use Session IDs: Instead of referencing direct object IDs like 1009, use secure, randomized session IDs to prevent guessing.

I hope this blog helped you understand IDOR. Stay tuned to know how we can further automate the process. Feel free to share your thoughts in the comments — what can be improved, and what topics you’d like to see covered next!