ProSiebenSat.1 issued the warning last night: "We have ascertained that there was recently unauthorized third-party access to one of our systems. The possibility that your data (email address and password) has been accessed by an unauthorized third party cannot be excluded. We were able to detect the problem promptly and took all necessary action to rectify the issue."
The company said that account data are encrypted and issued instructions how to change your password if this impacts you.
No European SOE PlanetSide 2 accounts were affected by the intrusion.
[Thanks to the mighty Tandor for the tip!]
[We've updated the article to clarify that only some PSS1 accounts were affected. SOE's European accounts are in the clear.]