When a merchant adds a crypto payment gateway, the most security-sensitive code is usually not the checkout button. It is the webhook handler that marks an order as paid. If that endpoint trusts whatever it receives, anyone who discovers the URL can mark orders as paid.

Source: [Dev.to](https://dev.to/pandawm/verifying-crypto-payment-webhooks-an-hmac-checklist-for-merchant-developers-iae)

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