In OxygenOS before 4.0.3 on OnePlus 3 and 3T devices, an unauthorized attacker can cause a locked bootloader to partially dump the ciphertext content of an arbitrary partition (except 'keystore') by issuing the 'fastboot oem dump <partition>' fastboot command.
With OxygenOS before 4.0.3, when a charger is connected to a powered-off OnePlus 3 or 3T device, the platform starts with adbd enabled. Therefore, a malicious charger or a physical attacker can open up, without authorization, an ADB session with the device, in order to further exploit other vulnerabilities and/or exfiltrate sensitive information.
An issue was discovered in OxygenOS before 4.0.3 for OnePlus 3 and 3T. The attacker can persistently make the (locked) bootloader start the platform with dm-verity disabled, by issuing the 'fastboot oem disabledmverity' command. Having dm-verity disabled, the kernel will not verify the system partition (and any other dm-verity protected partition), which may allow for persistent code execution and privilege escalation.