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## Summary The first-party PraisonAI A2A server example combines three behaviors into a remotely exploitable Critical chain: 1. The example exposes an A2A server without configuring `auth_token`. 2. The same example binds the server to `0.0.0.0`. 3. The example registers a `calculate(expression)` tool implemented with Python `eval(expression)`. An unauthenticated network client can send a JSON-