Guardrails And Safety hard
An agent's fetch_url tool is restricted to an allow-list of domains, and the check validates the hostname of the URL the model supplies. An injected document points the agent to an open redirect on an allow-listed domain. That redirect forwards to an attacker host carrying data in the path, and a variant forwards to 169.254.169.254. What closes the hole?
- A Match allow-listed hosts with a strict suffix rule so that lookalike hosts such as docs.company.com.evil.io are rejected outright.
- B Strip query strings from every URL before fetching so the model cannot append sensitive data to an outbound request.
- C Disable automatic redirects and re-validate each hop's host and resolved IP against the allow-list before following it.
- D Have the model restate the destination URL before each fetch so a second reasoning pass can catch suspicious redirects.
Answer: C. Disable automatic redirects and re-validate each hop's host and resolved IP against the allow-list before following it.
A check on the initial URL is bypassed by redirects and DNS tricks, so every hop and every resolved IP must be validated, with private and metadata ranges blocked. The cost is extra latency and broken legitimate redirect chains, such as link shorteners. Suffix matching is a real hardening step against lookalike domains, but it never sees the redirect. Stripping query strings fails because data can ride in the path.
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