In this paper, we present FETT, a fault injection tool for educational and training purposes addressed to educators and students in cybersecurity. Our tool aims to analyze and inject vulnerabilities into existing Django web applications for education purposes. Indeed, security education often relies on either abstract theoretical instruction or overly simplistic examples. This tool bridges the gap between theory and practice by modifying real web applications in a targeted, reproducible way. With its user-friendly interface and modular vulnerability injection, instructors can create challenges tailored to specific learning goals, while students engage directly with code that simulates production-level vulnerabilities. We evaluated FETT based on five publicly available GitHub projects and six student projects from the last three academic years (2022-2024). We successfully managed to efficiently inject vulnerabilities inspired by the OWASP top 10:2021 while keeping the core functionalities of the target application operational.