Simple press hacked??

Hi, I am a little worried about something that has come up on my Simple Press forum on this page http://www.bilingvni-vychova.com/forum/ Next to “Nechcete se zaregistrovat
hoste?” / “Do you want to register?” there is this “(Katka)” – I have no idea how it got there??? It was never there before… I can’t see anything else suspicious but this is making me a bit uneasy and worried. Any ideas anyone? Does it mean I’ve been hacked somehow or what?