Incident Dossier

Payment dedupe ignores amount mismatch

A mobile client retries the same idempotency key but the user has updated the amount in the meantime. The server happily returns the original payment receipt and never tells the operator that the second request asked for a different amount.

Initial failing signalRetry with mismatched amount returns the original responseExpected behavior: store.replay(mismatchedParams) throws IdempotencyMismatch · actual behavior: store.replay(mismatchedParams) returns the original response

Progress

1Reproduce the bugRun checks

2Edit the fixOpen

3Pass checksOpen

4Submit fixOpen

Reproduction Steps

Run npm test.
Remember a response for an idempotency key with params {amount: 4200}.
Replay the same key with params {amount: 8400}.
Add a payload comparison that raises on mismatch.

Focus Mode

Start

src/payment.js

Likely area

src/payment.js

Challenge Coach

Hints reveal broad direction first, then narrow toward the suspect path without showing hidden tests or exact solution code.

TopicData Integrity

DifficultyMedium

Est. time20 min

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workspace

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