Authentication bypass via doubled inherited middleware paths

Authentication bypass in Fastify @fastify/express 4.0.4 and earlier allows remote attackers to access protected child-plugin routes via ordinary requests. The onRegister hook re-registers an already prefixed parent middleware path through use(), which prepends the child prefix again. A default-configured Fastify 5.x application is exposed when path-scoped middleware protects a child plugin whose prefix overlaps that path, allowing unauthenticated reads or writes permitted by the skipped control.