Check XSS is a Firefox plugin designed for web development and security professionals. It simplifies the process of testing for vulnerabilities such as Cross-Site Scripting (XSS), CRLF injection, and SQL injection by providing a context menu with various payload options. Users can easily select a desired payload, which is then copied to the clipboard for quick pasting into input forms on any website. This functionality streamlines the testing process, making it more efficient for security engineers.

The plugin is subscription-based, catering specifically to developers and IT professionals who require a reliable tool for vulnerability assessments. By offering a straightforward interface and essential features, Check XSS enhances the workflow of users involved in web security, allowing them to focus on identifying and mitigating risks effectively.