Definition
Cross-site scripting, or XSS, is a type of web security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users. These scripts can execute in the victim's browser, enabling attackers to steal sensitive information, hijack user sessions, or deface websites. XSS attacks typically occur when an application takes untrusted data and sends it to a web browser without proper validation or sanitization. For instance, an attacker might post a comment containing a malicious script on a forum, and when another user views that comment, the script runs in their browser. This differs from SQL injection, which targets the database rather than the user's browser. Understanding XSS is crucial for cybersecurity professionals and is a common topic on exams like CompTIA Security+ and CySA+.