a convenience and not a truly secure method. There is a similar article about an iPhone that has made the internet rounds just recently.
OnePlus 6 Face Unlock Feature is fooled by the photo but OnePlus 5T is not any solution or any OnePlus 5T software part can be installed in OnePlus 6 to avoid this problem.
Moderator note: Site promotion disabled by moderator edit.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic