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Signature and replay-window gate
The product gate requires verifying a signature and setting a replay window before any webhook event is considered valid or status-updating. Unsigned or stale events are treated as failed and do not trigger any ledger changes.
Accepting unverified or delayed webhook payloads exposes prepaid accounts to forged balances and replay-driven double debits. You must enforce an upfront gate that cryptographically validates signatures and drops any payload timestamped outside a strict tolerance window before mutating funds. Related: Webhook signature and replay window, Inbound webhook retries, Shared status language for product and finance, Debit rows vs delivery status ledger.
Signature verify is a money gate
Money and status truth start only after the signature check passes. Missing, mismatched, or skipped signatures fail closed — no ledger row, no "delivered anyway for the pilot." Catalog Live does not waive the gate. Habits depth: Webhook signature and replay window. Soft USD 1,000/month treats "accept unsigned in staging forever" as production debt; USD 20 proves one forged body never posts a debit.
Replay window before status truth
| Gate check | Pass means | Fail means | |
|---|---|---|---|
| Signature present + valid | Authenticated event | Reject; no money/status write | |
| Timestamp inside window | Fresh enough to trust | Reject as replay/stale | |
| Event ID not seen | First accept | ACK without second debit | |
| Contract event listed | In buyer event menu | Drop unknown type | . |
At-least-once delivery will retry. A late retry outside the window is not "maybe delivered." Log window rejects separately from signature fails. Inbound retry depth: Inbound webhook retries.
Fail closed when the gate rejects
Rejected events never invent success. Product and finance share the same reject words — not hero upstream codes: Shared status language for product and finance. Debit rows stay aligned with accepted events only: Debit rows vs delivery status ledger. Side effects after ACK only; CRM work before the gate manufactures double truth.
Product, finance, and ops share one proof
Product: Can a legitimate signed, in-window event update status once? Finance: Does every money-affecting event show gate pass on the same UTC window? Ops: Export signature fails vs window rejects without Slack archaeology? Soft volume language stays blocked until the duplicate-in-window smoke shows one ledger line.
Buyer checklist for the signature replay gate
- Signature middleware on every production consumer before paid traffic? 2. Replay window named, logged, and bounded — not "weeks"? 3. Gate reject never writes money or success status? 4. Duplicate in-window event ID → one end state, no second debit.
Start with IOSOR
IOSOR is white-label prepaid. USD 20 funds a gate pilot on one consumer; soft review near USD 1,000/month prices skips verification as forged-status risk. Clients see white-label reject macros only.
IOSOR takeaway
Soft review of USD 1,000/month plans treats accepting unsigned events in staging indefinitely as production debt. A USD 20 pilot demonstrates that a single forged event body does not trigger a debit entry.
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