Cockpit-machines: cockpit-appstream: vnc console password disclosure through virt-xml command-line arguments

A flaw was found in cockpit-machines. When saving Virtual Network Computing (VNC) console settings, the configured password is passed directly as a command-line argument to an underlying system utility. A local unprivileged attacker on a host that allows cross-user process inspection could read the exposed password from the process list while another user modifies settings. This credential disclosure can allow unauthorized access to the guest virtual machine's graphical console.