Not really what common law is. At least not my understanding of the term. Law pre-exists the state and doesn't require a monopoly on violence. Many anarchists have written about this for many years.

I hear what you are saying though... but theft is a pretty universally accepted wrong. Even the way you are describing what happened sounds like theft to me. Its like saying the lock on my door was weak so it was ok that someone came in and took my computer. Its not.

That said, criminals steal from one another all the time. I'm not super concerned about what happened to ByBit. Unless I'm missing something... its theft and the moral hazard I read in your logic is a much bigger threat if it were to take hold. Its the kind of moral relativism that makes people think they are heroes for doing wrongs. But maybe I'm reading to much into it.

Edit:

So maybe I'm missing what you are saying. Sounds like you are saying the contract was not violated, but a flaw was found, IE the contract was not violated. Maybe, in that case its not theft. Still feels like it though.