I got "Your device is corrupt. It can't be trusted and may not work properly" on a brand new Nexus 5X. What should I do? Through Project Fi of Google, I ordered and got a brand new Nexus 5X with Android 6.0 on it.  The first time it powered up, it said

Your device is corrupt. It can't be trusted and may not work properly.


Although I can still use the phone, every time I restart or turn on the phone, the above message will show for a few seconds.

What can be done?
Unlocked bootloader = yellow triangle warning; modified system/kernel = red triangle warning.

As long as the device functions fine you shouldn't worry much; however if restoring is what you need, then flash a factory image then relock bootloader. Do turn on "OEM unlocking" in Developer options after that, so that you have a chance to recover in case anything happens.