Hacker only accessed plugin.php?

[Spangle]

I would echo what Zachery says, but you also need to check your public_html file for any files they may have added, I got hacked yesterday and thy tried to hide a couple of files, one was called "mail.php", the other was "passwords.txt"

I have also been notified by Hawkhost that there is a known exploit in Forum runner, so if you are using that it would probably be best to uninstall and delete any files belonging to it as well.