A British Galaxy S10 user has claimed that this phone's ultrasound sensor could be fooled into unlocking for non-registered fingerprints. This issue was allegedly caused by a cheap gel case with a clear flap to cover the screen. Samsung has admitted that this is the case, and has stated that it will push a software fix for it shortly.
https://www.notebookcheck.net/Samsung-Galaxy-flagship-fingerprint-sensors-are-reported-hackable-using-cheap-screen-protectors.439840.0.html