How to verify and secure configuration of OpenShift AI Gateway for Model Serving

Issue

Gateway API listener configurations using allowedRoutes.namespaces.from: All allow any namespace on the cluster to attach HTTPRoutes to the corresponding hostname managed by the Gateway.
This enables route hijack attacks: a user with standard namespace-level permissions can create an HTTPRoute that intercepts traffic intended for a legitimate model endpoint. Intercepted traffic includes API keys, user prompts, and model responses. The attack requires no elevated privileges and produces no visible errors for legitimate users.
Previous versions of Red Hat OpenShift AI documentation and upstream examples used this insecure default.