I clearly have been living under a rock, but in the case where it's just text in/out of their API, and a customer uses this on their own to do nefarious things, I don't see why they would be liable?
If they knowingly allowed use of their services for illegal purposes then yes, but in so far that they provide a service that can be used for useful things (including cyber security research) and did a best effort attempt at abuse, I don't see why it should make sense to hold them liable. This is especially the case now that frontier LLMs are almost a commodity that can be used without restrictions from providers outside of your legal jurisdiction.
If they knowingly allowed use of their services for illegal purposes then yes, but in so far that they provide a service that can be used for useful things (including cyber security research) and did a best effort attempt at abuse, I don't see why it should make sense to hold them liable. This is especially the case now that frontier LLMs are almost a commodity that can be used without restrictions from providers outside of your legal jurisdiction.