Vibe codingHardvc-g516

Subject Ai code reviewLevel Senior–Staff~20 minCommon in Security interviewsIndustries Software development, Technology

Question

This Lambda (JavaScript) authorizer caches the decoded token at module scope to skip re-verification on warm invocations. The AI claimed it's a performance win. A pentester escalates privileges with it. Explain the vulnerability.

1let currentUser = null;2 3exports.handler = async (event) => {4  if (!currentUser) {5    currentUser = verifyJwt(event.headers.authorization);6  }7  return {8    principalId: currentUser.sub,9    policyDocument: allowPolicy(currentUser.scopes),10  };11};

What a strong answer looks like

Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it — tests, edge cases, reading critically — and how you’d re-prompt or decompose to get it right.

Learn the concepts

Describe your solution

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.