qsfuzz (Query String Fuzz) is a security testing tool designed for fuzzing query string parameters in web applications. The tool allows security professionals to create custom rules for testing query string vulnerabilities. Users can define their own fuzzing patterns and payloads to systematically test web application parameters. qsfuzz focuses specifically on query string parameter testing, enabling researchers to identify potential security weaknesses in how web applications handle URL parameters. The tool supports rule-based fuzzing approaches, allowing for targeted testing of specific parameter types or vulnerability classes. The application provides a framework for automated query string manipulation and vulnerability discovery through systematic parameter fuzzing techniques.