TypeBot is a chatbot builder tool. In version 3.16.1, an authenticated user who has read access to any typebot can resume a WhatsApp preview webhook session that belongs to a different typebot by mixing an authorized typebotId and blockId and a foreign preview phone number tied to another preview session. The WhatsApp test-webhook handler authorizes the parent typebot first, but then resolves the preview chat session only by wa-preview-{phone}. As a result, an attacker can inject arbitrary webhook JSON into another workspace's WhatsApp preview session and advance its draft/unpublished flow without any access to the victim typebot. Version 3.17.0 patches the issue.