The hardware wallet implementations using the monero wallet do not check the unlock time when signing. This allows malware on the user's computer (which the hardware wallet should protect from) to permanently lock-up all the user's funds if the user signs a transaction on the device with a very high unlock time.To provide a scenario for this kind of attack: A disgruntled employee can use this vector to permanently cripple a business' funds.
https://hackerone.com/reports/817245