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December 7, 2022
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.
1. Log in to the application and add any juice to the basket while capturing the request using Burp Suite (or any other proxy).
2. Observe the application was making a request to GET /rest/basket endpoint and send a request to a repeater for later use.
3. As you can see, the Apple juice we have added previously to our basked has a basket ID 1
4. Now, modify the basket ID number from 1 to 2.
5. Again modify the ID from 2 to 5.
Observe that by modifying the ID number in an incremental fashion, we successfully exploited the BOLA vulnerability that allowed us to retrieve other users’ basket information. This happened because the basket endpoint above had a broken authorization flaw.
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.
In the next blog, we will learn how attackers can exploit BOLA by using other users’ unauthorized UUID.