What is Cross Site Scripting (XSS)?

Cross-Site Scripting (XSS) is a type of security vulnerability that allows an attacker to inject malicious scripts into websites viewed by other users. These scripts can execute in the user's browser and can be used to steal sensitive information like cookies, hijack user sessions, or deface websites. XSS attacks typically occur when a web application does not properly sanitize or encode user-supplied input before displaying it. This allows an attacker to inject malicious JavaScript or HTML code into the application's output, which is then executed by the victim's browser.