delivery.contact_changed
You corrected the recipient's e-mail address or phone number, or set their postal address. data. says which, and data. the channels the invitation went out on again. The addresses themselves are never in the event.
Receiving it
Subscribe a webhook endpoint to delivery.contact_changed, or to every type. Check the Parasend-Signature header before you trust the request (see Receiving webhooks), answer 2xx quickly, and fetch the resource for its current state.