XSSer, also known as Cross-Site Scripter, is a robust, open-source penetration testing tool designed to detect, exploit, and report Cross-Site Scripting (XSS) vulnerabilities in web applications. Built for security researchers and ethical hackers, it automates the process of identifying XSS flaws, including reflected, persistent, and DOM-based vulnerabilities. XSSer is pre-installed on Kali Linux, a leading penetration testing distribution, and supports multiple platforms like Ubuntu, ArchLinux, and Fedora. With features like payload customization, firewall bypass techniques, and detailed reporting, XSSer is a go-to tool for assessing web application security.