"Samsung Electronics is aware of the case of the S10's malfunctioning fingerprint recognition and will soon issue a software patch," the company told Reuters in a statement. The problem has been deemed serious enough that an online bank in South Korea, KaKaobank, has advised owners to switch off fingerprint recognition until it's resolved.
It's not clear what's causing the problem, but the Galaxy S10 uses an ultrasonic sensor to detect fingerprint ridges. Plastic or silicone screen protectors can stymie it, so Samsung has been recommending that buyers used approved protective devices. That doesn't explain why the system is allowing access to non-registered fingerprints, however. Engadget has reached out to Samsung for more information.
Samsung originally told UK publication The Sun, which first reported the problem, that it was looking into it. Until a patch comes, you could use Samsung's face unlocking, but that has had its own issues. For now, maybe just use a good old code.
Update 10/17/2019, 5:52 AM ET: A Samsung spokesperson gave Engadget the following statement: "We're investigating this internally. We recommend all customers to use Samsung authorized accessories, specifically designed for Samsung products."