The Vonage Messages API is an excellent tool for sending and receiving messages over various channels such as WhatsApp, Facebook Messenger, Viber, SMS, and MMS. To secure webhooks sent from the Messages API, authentication with JSON Web Tokens (JWT) and payload validation are crucial measures to prevent malicious actors from impersonating legitimate users or falsifying message statuses. Vonage uses HMAC-SHA256 tokens for JWT Bearer Authorization, which can be verified using a shared secret between the developer and Vonage. Payload validation involves checking the payload hash claim in the decoded JWT with the SHA-256 hash of the incoming message body to prevent token replay attacks. Additionally, verifying the "issued at" timestamp helps detect stale tokens. By implementing these security measures, developers can ensure secure webhooks for their applications.