What is the initial step that a webhook handler should perform upon receiving an event?

When a webhook handler receives an event, the crucial initial step is to validate the webhook signature. This validation ensures that the event is genuinely coming from the legitimate source and has not been tampered with during transmission. Stripe and other webhook providers include a signature in the event request headers that can be verified using a secret key. By performing this validation first, the handler can confirm the authenticity of the event before processing it further or executing any business logic.

If the signature cannot be validated, it is unsafe to trust the data and the event can be ignored or logged for further investigation. This step acts as a safeguard against malicious attacks and ensures the integrity of the data being handled.

While parsing the event data, logging it, and storing it in a database may also be necessary steps in processing the webhook, they should only occur after the webhook's authenticity has been confirmed through signature validation. Thus, signature validation is rightly positioned as the most critical initial action in handling incoming webhook events.