Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS) is one of the most prevalent web vulnerabilities. It occurs when an application includes untrusted data in a web page without proper validation or escaping, allowing attackers to execute malicious scripts in the victim's browser.

XSS attacks can steal session tokens, redirect users to malicious sites, deface websites, and perform actions on behalf of the victim. Understanding XSS is essential because it is both common and impactful, affecting millions of websites worldwide.

This chapter covers the three main types of XSS attacks, how they work, and comprehensive strategies for preventing them.