User ID controlled by request parameter, with unpredictable user IDs

Access Control Vulnerability

In the world of cybersecurity, access control vulnerabilities remain one of the most dangerous and prevalent issues in modern web applications. One such vulnerability that often slips under the radar is the User ID controlled by request parameters, which attackers can exploit to gain unauthorized access to sensitive information. However, a critical solution to this issue involves the use of unpredictable user IDs, which significantly raise the barrier for attackers trying to manipulate or guess the IDs.

Let’s explore why this vulnerability is so dangerous, how attackers exploit it, and how using unpredictable user IDs can protect your application.

Many web applications identify users based on URL or request parameters like user_id. These parameters are often used to retrieve a specific user’s profile, order history, or personal data. For example, an e-commerce site might include a URL like this:

https://shoponline.com/account?user_id=10234