This is industry standard. Flashing old updates that are insecure to bypass security is a legitimate attack vector that needs to be defended against. Ideally it would still be possible up recover from such a scenario by flashing the latest update.

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digiown 2 hours ago | parent | next [-]

Standard?? The standard is for the upgrade to be refused or not boot until you flash a newer one, not to brick the phone permanently. It's not an "ideally" thing for the manufacturer to not intentionally brick your device you bought and paid for.

	▲	charcircuit 24 minutes ago \| parent \| next [-]
		>and you may damage your device permanently https://service.oneplus.com/us/search/search-detail?id=op588 They make it clear that this feature is unsupported and it's possible to mess things up. The reason why it's an ideal and not an expectation is that flashing alternate operating systems is done at one's own risk and is unsupported. They have already told the users that they bear no responsibility for what may go wrong if they flash the wrong thing on that device. Flashing incompatible operating systems to the device requires people to be careful and proper care to ensure compatibility before going through with flashing was not done.
	▲	38 minutes ago \| parent \| prev [-]
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orbital-decay 4 hours ago | parent | prev [-]

What's being attacked in this particular case?

	▲	charcircuit 3 hours ago \| parent [-]
		The phone. It's the same attacks that secure boot tries to protect against. The issue is that these old, vulnerable versions have a valid signature allowing them to be installed.