What does cross-site scripting (XSS) refer to?

Cross-site scripting (XSS) refers to a security vulnerability that allows an attacker to inject malicious scripts into web pages viewed by other users. This typically occurs when a web application does not adequately validate or sanitize input provided by users, allowing harmful code to be executed in the context of a user's browser session. When a user unknowingly visits a compromised webpage, the injected script can execute, potentially leading to data theft, session hijacking, and other malicious activities.

Understanding XSS is crucial because it highlights the importance of web security practices, including user input validation and implementing Content Security Policies (CSPs) to mitigate such vulnerabilities. The other options mention unrelated concepts: improving loading speed, encrypting data, and enhancing navigation do not pertain to the nature or implications of XSS.