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AI Security

Interview question · Identity, OAuth & Access Control

Your API accepts JWTs from several identity providers. How do you validate them so one issuer cannot impersonate another's users?

Each token verifies against some trusted key. The bug is that the key belonged to a different issuer than the one the token claims, or the user ID means something different there.

hardNewPreparation tags: Microsoft, Google, AmazonUpdated Nov 2026

Each token verifies against some trusted key. The bug is that the key belonged to a different issuer than the one the token claims, or the user ID means something different there.

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  1. 01 State the assumptions your answer depends on.
  2. 02 Explain the mechanism and choose a control.
  3. 03 Name a condition that would change your decision.

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What if · the follow-ups in this answer

The answer works through 6 follow-ups like an interviewer would

An API accepts JWTs from three identity providers used by different enterprise customers, and currently looks up keys from whatever issuer the token names.

  1. Why is looking up keys from the token's issuer risky?
  2. How should keys be selected?
  3. Which claims must be checked?
  4. How should users be identified?
  5. How do you test the validation?
  6. What validation design would you implement?

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