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Unpatchable AMD Chip Flaw Unlocks Paid Tesla Feature Upgrades
(www.tomshardware.com)
This is a most excellent place for technology news and articles.
Even if it is in the contract, it's not enforceable (depending on country). In a fair few, the manufacturer has to prove that the modifications caused the defect to invalidate the warranty.
It's unclear what would happen if they simply refused to service the car, or bricked it instead.