Webhook Signature Verification (HMAC-SHA256) in Node, Python, Ruby — 2026 Guide

I review a lot of webhook handlers. Roughly 3 out of 5 either have a subtle signature-verification bug — or someone disabled verification entirely "to make it work." Both leave a public POST endpoint that anyone with the URL can fire fake events at. If your handler refunds a customer, sends an email, or flips a feature flag, that's a real problem. This guide is the version I wish someone had handed me on day one: a single HMAC-SHA256 verifier in Node, Python, and Ruby — plus the 6 specific gotch