what the vendor says
Publishes no source-IP list of its own; states 'Stytch's webhooks are powered through Svix'. A receiving endpoint allowlists the svix service in this feed instead. Their own IP feature runs the other way: up to 10 customer IPs that may call the Stytch API, arranged over email with support.
Source: https://stytch.com/docs/b2b/guides/webhooks. That page is where this entry comes from, so you can check it rather than take our word for it.
who sends this traffic
Stytch's webhooks are delivered by Svix, and Svix publishes the addresses it sends from. Those ranges are in the catalog, so the delivery side can be pinned even though this vendor lists nothing itself. They belong to the delivery provider, which means they cover every product built on it rather than this vendor alone.
what to do instead
Pick the control the vendor actually supports, and keep it scoped to the one workload that needs it:
- Verify the message, not the sender. Where a vendor signs its webhooks, checking the signature is stronger than an address check would have been, and it survives their infrastructure changing.
- Allow the hostname. Where a vendor publishes a stable domain, that needs something which resolves names: a proxy, a DNS firewall, or a network firewall rule group. A security group cannot do it.
- Contain the blast radius. Give that workload its own security group so the broad rule lives there and nothing else in the account inherits it. Coverage has a worked example.
the rest of your stack
One unpinnable dependency does not stop you pinning the others. The catalog covers the vendors that do publish official ranges, and the vendor report scores how well each one publishes.