https://www.theregister.co.uk/2018/06/12/oneplus6_smartphone_security_snafu/

The recently released ‪OnePlus 6‬ smartphone allows the booting of arbitrary images, security researchers at Edge Security have discovered.

According to the researchers, the trick is possible using the fastboot boot image.img feature on the BBK Electronics phone – even when the bootloader is completely locked and in secure mode, as the video embedded in a Twitter update here illustrated.