xmimox on "4.3.1 - System Hack or Plugins - help"

Hello.

I made some changes on a test website, at the moment its on a testserver.

I saw that the page was loading extreme slowly on other pcs, then i registered that the subpages opened 2 links (beyond this post).
The Code can be checked here: malware code from header.php

WordPress: 4.3.1 - clean install
Theme: newest version

Plugins:
Advanced Automatic Updates
AntiVirus
Contact Form 7
Duplicator
Pixo Simple SEO
SiteOrigin Widgets Bundle
Page Builder by SiteOrigin
Virtue/Pinnacle Toolkit

I dont know what i made wrong, whats the error?!
Where is my fail? All up to date.