"Cross-site scripting" (XSS) refers to a type of security vulnerability found in web applications that allows attackers to inject malicious scripts into webpages viewed by users. This occurs when an application does not correctly validate or encode user input, allowing unauthorized code execution within a user's browser. XSS can lead to data theft, session hijacking, and other malicious activities while compromising user privacy and security. Preventing XSS attacks requires diligent input validation, content security policies, and user education to ensure safer online interactions and protect sensitive information.