Cross Site Scripting (originally CSS but the acronym was changed to XSS to avoid confusion with Cascading Style Sheets), also known as an arbitrary script injection flaw, is a pernicious vulnerability in web applications. Noted in the OWASP Top 10 most common web application vulnerabilities XSS is an often misunderstood and overlooked. XSS can allow an attacker to take control of a victim web browser, often without leaving any trace of their attack. XSS targets web application users rather than the application server, as is the case in attacks leveraging SQL injection, authentication bypass, or code execution vulnerabilities. Because XSS vulnerabilities affect site users, rather than application infrastructure, it is often overlooked by developers or security officers. However, as the browser becomes closer to a complete operating system for many users it is becoming an increasingly attractive target, and platform, for attack.