Provider-credential-controller: provider-credential-controller: cross-namespace credential propagation via attacker-controlled copiedfrom labels bypasses authorization

A flaw was found in the provider-credential-controller component of multicluster-engine (MCE). An attacker with specific permissions on the hub cluster, and knowledge of a prior credential value, could exploit an authorization bypass vulnerability. By manipulating `copiedFrom` labels, the attacker could intercept newly rotated provider credentials, leading to unauthorized information disclosure. This allows access to sensitive credentials that should otherwise be protected.