Backstage: Improper entity validation in deprecated Kubernetes services endpoint

Impact

An authenticated user with Kubernetes read permissions could access Kubernetes workload data beyond their intended scope by supplying crafted entity data to the deprecated services endpoint. The exposure is limited to read-only access to Kubernetes object metadata across configured clusters.

Patches

Patched in @backstage/plugin-kubernetes-backend version 0.21.8.

Workarounds

• Disable the deprecated /services/:serviceId route by deploying a custom Kubernetes router that omits it.
• Restrict access to the kubernetes.resources.read permission to limit the set of users who can reach the endpoint.