Once you moved to the Screen Lock screen, the app shows the available authentication method - either Face ID or Touch ID - that you can enable to lock your WhatsApp. Recently, a new bug on the WhatsApp Android app has been discovered which continues to save the last message that you have replied even after you have exited the app.
Hopefully this is an added layer of security that more messaging and social media apps will implement in the future.
This option can be accessed by navigating to Settings Account Privacy within the application and enabling the Screen Lock feature. Users are now able to restrict access to the app as a means of protecting private conversations with the help of FaceID or TouchID. There is no word as to when Android users will get the same.
The report also added that users can still reply to messages from notifications or receive WhatsApp calls without the need for authentication.
WhatsApp didn't immediately respond to a request for information about any new security for the Android version of the app. The app will also prevent users from checking the preview out in the multi-tasking window if and when the authentication feature is enabled.