Executive brief
TypeBot is a chatbot builder tool that allows users to create and test conversational workflows. In version 3.16.1, an authenticated user with read access to one chatbot can hijack and manipulate WhatsApp preview test sessions belonging to different chatbots, potentially injecting malicious messages or advancing unpublished workflows without authorization. This could allow attackers to test or modify competitor bots or interfere with other users' development work.
Technical details
The vulnerability is an authorization bypass in the WhatsApp preview webhook handler. The application authorizes the parent typebot first but then resolves the preview chat session only by a phone number identifier (wa-preview-{phone}), creating a session collision vulnerability. An authenticated attacker can mix an authorized typebotId and blockId with a foreign preview phone number from another user's preview session to inject arbitrary webhook JSON and advance draft/unpublished flows. Attack preconditions include authentication (as any user with read access to any typebot) and network access to the webhook endpoint. The patch (version 3.17.0) validates that preview sessions belong to the authorized typebot and enforce that the session is waiting on the requested webhook block.
Affected products
- TypeBot TypeBot 3.16.1
Timeline
- 2026-08-11: disclosed
- 2026-05-21: patched: Version 3.17.0 includes the fix