I'd love to know what airline it is (I guess we'll find out soon).
Air New Zealand just sent the following email out so I guess it's not them:
We have recently been alerted that a Star Alliance partner has been impacted by a security data breach, involving some of our customers’ data as well as that of many other Star Alliance airlines.
The Star Alliance member airlines share minimal frequent flyer data between each other and limited third parties to ensure benefits can be used across different carriers, for example access to member lounges.
Unfortunately, some of your information has been involved in this data breach however, this is limited to your name, tier status and membership number. This is the full extent of frequent flyer data Air New Zealand shares with other Star Alliance member airlines.
This data breach does not include any member passwords, credit card information or other personal customer data such as itineraries, reservations, ticketing, passport numbers, email addresses or other contact information.