Fastify is a web framework with minimal overhead and plugin architecture. The attacker can use the incorrect "Content-Type" to bypass the "Pre-Flight" checking of "fetch". "fetch()" requests with Content-Type’s essence as "application/x-www-form-urlencoded", "multipart/form-data", or "text/plain", could potentially be used to invoke routes that only accepts "application/json" content type, thus bypassing any CORS protection, and therefore they could lead to a Cross-Site Request Forgery attack. This issue has been patched in version 4.10.2 and 3.29.4. As a workaround, implement Cross-Site Request Forgery protection using `@fastify/csrf'.