Why can't you change it once you know the adapter was shipped with a tracking number. Seems there is no reason for your buyer to get into your Tesla account once they ship to you.
A certain level of caution is always smart. But I think people are over-thinking this a little.
When you supply a credit card number to any retailer, at some point you have to trust that they will not steal your money.
In this case, you don't directly provide access to a source of money (or at least I didn't by using PayPal), but just access to the Tesla system.
My understanding was that Harumio didn't want the password changed until they received the adapter from Tesla. (If a purchase had been cancelled as happened early on with North Americans trying to buy directly from Tesla-Korea, I suspect Harumio would have tried again using various tactics, no doubt, to achieve a successful purchase on behalf of the customer.) After the adapter was received by Harumio, it was OK to change passwords, correct? (Maybe I have that wrong?)
Regardless, it is relatively easy to check your Tesla-Korea account (using Google for translation purposes) to make sure no other products were purchased. If additional purchases were made, they wouldn't have used your money anyway. But I have heard of no such occurrence. Nonetheless people should do that (check), and change their password to prevent it anyway. (Didn't Harumio itself advise that?) And I recommend the use of PayPal (or other secure payment procedure).
In conclusion, so far Harumio has given every indication of being trustworthy. I have heard no complaints. Until or unless that changes, I think we should stop being paranoid and take advantage of this beneficial service--albeit one that probably costs more than the eventual direct retail sales of the adapter will in North America--whenever that occurs. We are paying a service company for early access to something we wouldn't normally have. People who remain concerned should probably avoid making the purchase and simply wait for the inevitable release of the adapter in North America.