Plesk default page returning every time

[eladleev]

Hey there,
I'm not using any vhost, all my site files are in /var/www/vhosts/default/htdocs.
Every few days the default Plesk page (html and img folder) returns and "take control" of the site.
I'm using WordPress, so I have a index.php file, so if the Plesk's index.html file returns he's shown in the site instead of the .php file.
What can I do to make sure that that Plesk's files won't come back?]
Thanks!