CVE-2026-73266: Clusterclaims-controller: clusterclaims-controller: tenant-controlled clusterclaim labels propagated to managedcluster enabling cross-tenant managedclusterset join

A flaw was found in the clusterclaims-controller component of Multicluster Engine (MCE). An authenticated tenant can exploit this vulnerability by manipulating ClusterClaim labels. This allows the tenant to force a cluster to join a ManagedClusterSet belonging to another tenant. Such unauthorized access could enable the injection of policies and workloads into other tenants' clusters.