Glossary · Phase 9 · Model Context Protocol
Confused deputy
A program with some authority tricked into using it for someone who shouldn't have it, such as by forwarding a token.
Your server would then accept tokens meant for someone else, which skips the audience check. And downstream systems would see a request that seems to come straight from the client, with your server's checks bypassed. That's a confused deputy: a trusted helper tricked into using its authority for someone else.
Try it now
Note the audience check: a token meant for one server must not work on another.
Learn it properly
Securing remote servers with OAuth · Protected resource metadata, PKCE, audiences and scope challenges. About 45 minutes.
Other terms from the same lesson
- token passthrough: Forwarding a token a client sent you to another service. MCP forbids it; get your own token for each service instead.
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