In modern smartphones, screen fingerprint scanners are increasingly popular. Most consider this method of authentication to be the most convenient, if not the fastest. However, the technology of combining the display with a fingerprint scanner has one drawback, which until recently was not known.
Xiaomi sub-screen fingerprint scanner can be used as a camera
It was discovered by one of the enthusiasts who shared his discovery on the Reddit forum. He claims that in the hidden system settings of the Xiaomi Mi 9T, he discovered the ability to view what the micro-camera of the optical fingerprint scanner captures. In support of his words, he posted a video demonstrating this “feature” on the forum. You can watch the video below.
A Redditor found a hidden activity on a Xiaomi phone that lets you see the raw feed from Goodix's optical under-display fingerprint scanner.https://t.co/RKpjDTdgzG
OEMs really shouldn't be leaving these debug apps in production builds… pic.twitter.com/fnEpvPZtol
— Mishaal Rahman (@MishaalRahman) August 10, 2020
The image quality and resolution are far from perfect, so you won’t be able to see anything. But despite this fact, the member of XDA-Developers portal, Mishaal Rahman, believes that this is a dangerous vulnerability that must be blocked. He argues that this flaw has nothing to do with the security of the sensor itself. The problem is in the firmware itself.
At the moment, Xiaomi has not reacted in any way to the discovery and there is no information whether it will patch the flaw in its devices that has display fingerprint scanners.
It is worth to mention that Xiaomi has been using in-display fingerprint scanners in several devices of the mid-range and high-end categories, and among them, the popular Mi 9T, the hero of this discovery. The smartphone has been released in the summer of last year and here is a reminder of its specification.
Xiaomi Mi 9T specifications
- 6.39-inch (2340 × 1080 pixels) Full HD+ 19.5:9 aspect ratio AMOLED HDR display with 103.8% NTSC Color Gamut, 600nit (HBM) / 430nit (Typ) brightness, Corning Gorilla Glass 5 protection
- Octa Core (2.2GHz Dual + 1.8GHz Hexa) Snapdragon 730 Mobile Platform with Adreno 618 GPU
- 6GB LPDDR4X RAM with 64GB / 128GB (UFS 2.1) storage
- Android 9.0 (Pie) with MIUI 10
- Dual SIM (nano + nano)
- 48MP rear camera with Dual LED Flash, f/1.75 aperture, 1/2″ Sony IMX582 sensor, 0.8μm pixel size, 6P lens, 8MP 1/4″ telephoto lens with 1.12μm pixel size, f/2.4 aperture for 2x loss-less zoom, 13MP 1/3″ 124.8° ultra-wide sensor, 1.12μm pixel size, f/2.4 aperture
- 20MP front-facing camera with f/2.2 aperture, 0.8μm pixel size
- In-display fingerprint sensor
- 3.5mm audio jack, Qualcomm WCD9375 Hi-Fi audio chip
- Dimensions: 156.7x 74.3×8.8; Weight: 191g
- Dual 4G VoLTE, WiFi 802.11 ac (2.4GHz + 5GHz), Bluetooth 5, GPS + GLONASS, NFC, USB Type-C
- 4000mAh (Typical) / 3900mAh (Minimum) battery with 18W fast charging