What is the first step that a webhook handler should take when created?

Validating the webhook signature is crucial because it ensures that the incoming webhook request genuinely originates from Stripe and has not been tampered with during transmission. This step prevents potential security vulnerabilities by confirming the authenticity of the data being processed.

Once the webhook handler receives a request, the first action should be to compute the expected signature based on the payload and the secret provided by Stripe. This computed signature is then compared to the signature included in the webhook request header. If they match, it assures that the data is safe to process. If they do not match, it's clear that the request could be forged or altered, and the handler should reject the request without further processing.

The other options, while potentially useful in different contexts, do not address this vital security measure directly. Logging details could assist in troubleshooting or monitoring but does not contribute to checking the validity of the incoming request. Sending a confirmation message might be relevant for other types of interactions but does not fit the standard practice for webhooks. Checking the endpoint URL could be helpful in some contexts, but it still does not provide the validation needed to ensure the request's authenticity.