Is it forbidden for women to use the "iPhone X" which unlocks via facial recognition, fearing that Apple might save face images, and consequently their 'awrah (like hair) might be exposed to strangers?

The default ruling is the permissibility of using modern devices. However, a woman must not use the face recognition feature if it will reveal her hair or any part of her body that must be covered, due to the possibility of non-mahram (definition) men seeing her images and her data being leaked. She can suffice with a fingerprint or a secret passcode.