OxygenOS before version 4.0.2, on OnePlus 3 and 3T, has two hidden fastboot oem commands (4F500301 and 4F500302) that allow the attacker to lock/unlock the bootloader, disregarding the 'OEM Unlocking' checkbox, without user confirmation and without a factory reset. This allows for persistent code execution with high privileges (kernel/root) with complete access to user data.