Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS)

What is Cross-Site Scripting (XSS)?

Cross-Site Scripting (XSS) is a security vulnerability in web applications where an attacker injects malicious scripts into web pages viewed by others. This occurs when a web application does not properly validate or sanitize user input, allowing harmful code to execute in the victim's browser as though it were legitimate.

There are three main types of XSS: Stored XSS, where the malicious script is permanently stored on the server and affects every visitor to the page; Reflected XSS, where the script is reflected off a web server and executed immediately, often through a malicious link; and DOM-based XSS, which occurs entirely in the browser’s client-side code without server-side involvement.

Preventing XSS involves validating and sanitizing all user input, implementing a Content Security Policy (CSP) to control script sources, and escaping user input so it is treated as data, not executable code. Regular security audits are also essential for identifying and addressing XSS vulnerabilities.