Most operating websites experience a cyber-attack at some point. Cross-site Scripting (XSS) attacks are cited as the top website risk. More than 60 percent of web applications are vulnerable to them, and they ultimately are responsible for over 30 percent of all web application attacks. XSS attacks are complicated, and they often are used in conjunction with social engineering techniques to cause even more damage. Although prevention techniques exist, hackers still find points of vulnerability to launch their attacks. This project explored what XSS attacks are, examples of popular attacks, and ways to detect and prevent them. Using knowledge gained and lessons-learned from analyzing prior XSS incidents, a simulation environment was built using XAMPP and VirtualBox. Four typical XSS attacks were launched in this virtual environment, and their potential to cause significant damage was measured and compared using the Common Vulnerability Scoring System (CVSS) Calculator. Recommendations are offered for approaches to impeding XSS attacks including solutions involving sanitizing data, whitelisting data, implementing a content security policy and statistical analysis tools
