Last time I’ve logged into whatsapp Desktop app i just had to scan a bar code and that’s it i was logged in, but not now. Whatsapp has added another layer of security to win trust back from users. From now on WhatsApp users will be required to use biometric verification when singing into a new desktop or web client. The feature has been made available for both iOS and Android users.
When you authorize web or desktop client session from main phone a biometric authentication prompt will pop-up asking you to place finger on the scanner. Once the real owner of phone uses its fingerprint only then QR scanner appears on screen.
Whatsapp doesn’t have direct access to biometric verification, its only allowed to use it for identification purposes.