The issue of the ultrasonic fingerprint sensor, as explained by Samsung, occurred after certain owners of the Galaxy S10 began applying third-party “silicone screen protecting cases” – a screen protector, basically – on to the display of the phone. Upon doing so, the screen protector caused issues with the built-in sensor’s three-dimensional patterns, thus causing the phone to unlock even when the fingerprints were not registered on the phone.
Samsung also says that it is already planning on releasing software update that will fix the issue, albeit sometime early next week. However, it appears that Galaxy S10 owners will have to rescan their fingerprints once the phone is updated. Until then, Samsung is recommending owners of its Galaxy S10 series, as well as owners of the Galaxy Note10 and Note10+ to disable the feature, delete all currently registered fingerprints. (Source: Samsung Newsroom)
