kcp allows unauthorized creation and deletion of objects in arbitrary workspaces through APIExport Virtual Workspace

kcp is a Kubernetes-like control plane for form-factors and use-cases beyond Kubernetes and container workloads. Prior to 0.26.3, the identified vulnerability allows creating or deleting an object via the APIExport VirtualWorkspace in any arbitrary target workspace for pre-existing resources. By design, this should only be allowed when the workspace owner decides to give access to an API provider by creating an APIBinding. With this vulnerability, it is possible for an attacker to create and delete objects even if none of these requirements are satisfied, i.e. even if there is no APIBinding in that workspace at all or the workspace owner has created an APIBinding, but rejected a permission claim. A fix for this issue has been identified and has been published with kcp 0.26.3 and 0.27.0.