In this article, we will discuss an interesting test case where a weak user identifier can be used to perform a BOLA attack which could lead to data modification and sensitive data exposure. The attacker aims to compromise users' basket information.

General Severity:  Medium to Critical

OWASP Category: API1:2019 Broken Object Level Authorization

For practical demonstration, we will use Owasp Juice Shop vulnerable application. 

The web application has a feature where users can add their preferred juices to the basket. As an attacker, we will try to guess and retrieve information about other users by modifying IDs on the vulnerable REST API basket endpoint.

Impact:

Object references frequently include database IDs, which can be accessed by attackers to expose sensitive user information. You can also learn more about what BOLA is here.

Remediations:

1. Developers implementing the API should implement a proper authorization mechanism. In the above case, the developer should check if the requested basket id is actually owned by the user and only then allow access.
2. Perform active testing of your endpoints for BOLA vulnerabilities using automated testing products such as Akto. Do not deploy vulnerable changes that break the tests.
3. Always use the UUID instead of simple sequential number IDs. UUIDs are Unique identifiers IDs, a mixture of letters and numbers that are impossible to guess.

In the next blog, we will learn how attackers can exploit BOLA by using other users’ unauthorized UUID.