Toomuchmedia has released a security update for NATS 3. They told their clients to patch as soon as possible. NATS 4 (and higher) was not affected by the bug.
This security update was released only a few days after it became known that Lords of Porn, Vidz, Nice Ratios, Eurorevenue and other programs running NATS 3 were hacked and had their email list stolen.