Warning: some players have been using an unofficial version of the client and their accounts were hacked.
What happened: this unofficial version of the client included a cheat to automatically heal. This triggered Stendhal's bot detection scripts. Our scripts run periodically to analyse the logs. So after some time the accounts who used it were permanently banned. We did more investigation and noticed that the accounts who were banned, had also had their accounts accessed illegally - from another country.
Conclusion: this unofficial, self-healing version of the client, has a secret part which tells your password to the creator.
What you need to do: If you ever used this bot (and got banned), change all your passwords everywhere. Everyone else: please be careful and only run programs which come from trusted places.