Define the term "XSS" in the context of web application security.

The term "XSS" stands for "Cross-Site Scripting," which refers to a type of vulnerability found in web applications. This security flaw allows attackers to inject malicious scripts into web pages viewed by other users. When a user visits an affected page, the injected script can execute in their browser, potentially leading to a range of harmful activities, such as stealing session cookies, capturing keystrokes, redirecting users to malicious sites, or displaying deceptive content.

Understanding the significance of XSS is crucial in web application security because it emphasizes the need for proper input validation and output encoding to protect users from such attacks. Web developers must implement security measures, such as Content Security Policy (CSP) and frameworks that escape data before rendering it in a web environment. This knowledge helps safeguard both the application and its users from malicious exploitation.