https://wccftech.com/a-xiaomi-user-was-able-to-turn-fingerprint-sensor-into-a-functioning-but-horrendous-camera/

Optical fingerprint sensors have become commonplace for smartphones that are not using the more advanced ultrasonic fingerprint sensors. For those who don't know, these fingerprint sensors are essentially cameras that scan your fingerprint for the purpose of authentication. These are found in phones ranging from Oppo, Xiaomi, OnePlus, and even Samsung and they are moderately successful and risk-free, as well.

However, the recent revelation reveals that the optical fingerprint scanner on your phone might not be as secure as you may think, in the first place. As showcased by a Reddit user on their Xiaomi Mi 9T, users can access the imagining feed from the fingerprint sensor on the device and all they have to do is install an Activity Launcher app. A simple app that gives users access too hidden activities that are within their device.