Pods in your cluster can resolve internal service names (e.g., my-svc.default.svc.cluster.local) but all attempts to resolve external domains (e.g., api.github.com) return NXDOMAIN. CoreDNS pods are Running with no restarts, and the CoreDNS Service has valid endpoints. You inspect the CoreDNS ConfigMap and find that the 'forward' plugin line was recently edited. What is the MOST likely cause and the correct fix?