What is Cross-Site Scripting (XSS) and how can you prevent it?

Cross-Site Scripting (XSS) is a security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users. This can lead to data theft, session hijacking, and other malicious activities. To prevent XSS, you should validate and sanitize user inputs, use Content Security Policy (CSP), and escape data before rendering it in the browser.