Diggit Drupalextras

Yesterday I get my site "Hacked" (?). Mission and footer had changed places and all the pages in my books were spread around and was no longer a part of a book.
All my modules, core and the theme is updated. Are there any modules or anything else that makes an unsafe installation?
This is the third time my books are been changed, and all the times with Drupal 6, but with two different s hosts.