API-Based XSS: Persisted XSS via API Calls in OWASP Juice Shop

Web applications often expose backend APIs for client-server communication. These APIs can be a critical attack vector if they lack proper validation or sanitization. In this lab, you will exploit a vulnerability in the OWASP Juice Shop’s product API to perform a persisted Cross-Site Scripting (XSS) attack.

This lab demonstrates:

1. How to interact directly with an application’s API without using the frontend.
2. How improper input validation in APIs can lead to persisted XSS vulnerabilities.
3. The impact of persisted XSS attacks on web application functionality.

Objectives

Upon completing this lab, you will:

• Learn to identify and exploit API vulnerabilities for XSS attacks.
• Understand the risks of improper input validation in backend APIs.
• Recognize the dangers of bypassing frontend controls to manipulate server data directly.

Who is this lab for?

This lab is designed for:

• Developers looking to secure their APIs against XSS vulnerabilities.
• Security professionals seeking to understand XSS exploitation via APIs.
• Learners exploring advanced web application attack techniques.