Kite is a Kubernetes dashboard. Prior to version 0.12.3, authenticated Kite users with any role can request `/api/v1/overview` for a cluster that their roles do not permit by selecting that cluster with `x-cluster-name`. The overview route is registered before `middleware.RBACMiddleware()` and `GetOverview` only checks `len(user.Roles) > 0`, so it returns aggregate Kubernetes inventory and capacity data from unauthorized clusters. Version 0.12.3 fixes the issue.

Affected: Go: github.com/zxh326/kite

## Summary

Authenticated Kite users with any role can request `/api/v1/overview` for a cluster that their roles do not permit by selecting that cluster with `x-cluster-name`. The overview route is registered before `middleware.RBACMiddleware()` and `GetOverview` only checks `len(user.Roles) > 0`, so it returns aggregate Kubernetes inventory and capacity data from unauthorized clusters.

The issue is present on current main commit `38c9bb9d4b746c0d2a8252f3c35cdfa07ab01c21` and latest release `v0.12.2` at commit `0aae35abb2d6a8adf623fe60349261aa48753ccc`.

## Impact

A low-privileged user who only has access to one cluster can set `x-cluster-name` to another configured cluster and retrieve aggregate inventory and resource sizing data for that cluster. The response includes total node, pod, namespace, service, CPU, and memory values. This bypasses the cluster membership boundary used elsewhere in Kite.

The validated impact is confidentiality only. I did not prove Kubernetes mutation, pod names, secret values, kubeconfig contents, or bearer token exposure through this endpoint.

## Technical details

`routes.go` registers `/api/v1/overview` before the global RBAC middleware is applied:

- `routes.go:131-133`: `/api/v1` gets `RequireAuth()` and `ClusterMiddleware(cm)`. - `routes.go:135`: `/api/v1/overview` is registered. - `routes.go:171`: `api.Use(middleware.RBACMiddleware())` is applied only after overview and several other routes are registered.

`pkg/middleware/cluster.go:2…