Cross-Site Scripting (XSS) is one of the most prevalent and dangerous vulnerabilities in web applications. It allows attackers to inject malicious scripts into web pages viewed by other users, leading to a wide range of potential attacks. In this blog post, we will explore various scenarios where XSS might occur and provide a step-by-step guide to testing and identifying this vulnerability.

Cross-Site Scripting (XSS) occurs when an attacker injects malicious scripts into content that is then served to users. These scripts can steal information, manipulate web content, or redirect users to malicious sites. XSS vulnerabilities are categorized into three main types: Stored XSS, Reflected XSS, and DOM-based XSS.

Description: In a web application with a comment section, if user input is not properly sanitized, an attacker might inject a malicious script that gets stored in the database and executed when other users view the comment.

<!-- Attacker's Comment -->
<script>alert('XSS Attack!');</script>

Testing Method: Input the above script in the comment section and observe if an alert box appears when the comment is viewed.

Description: In a search functionality that reflects user input in the search results, an attacker might craft a URL with a malicious script that gets executed when a user clicks on it.

Example URL:

https://example.com/search?q=<script>alert('XSS Attack!');</script>

Testing Method: Access the above URL and observe if an alert box appears.

Description: In a language selector that uses JavaScript to update the page content based on user input, an attacker might manipulate the DOM to execute a malicious script.

Example URL:

https://example.com/home#lang=<scri…