Mass of returning visitors that stay 0 sec

lately in my site I saw a huge amount of returning visitors that just get into the site to one page, (not only the index) and stay there for (0s) and then leave.
it’s not 1 or 2, it’s more than 200 visitors like that…
I don’t have any outbound links in my site so the only way is to stay on my site.
Do you think that it’s a script problem? or maybe bots?


Please update to 1.7 beta where a bug causing this problem has been fixed: 301 Moved Permanently

I also faced that problem please notedown the time and date, after that check whether it is domain renewal date