OKAYFREEDOM_INJECTED

I use iTheme Security, but since some weeks i found in the code of each post at the end following statement:

 
<div id=”OKAYFREEDOM_INJECTED” style=”display: none;”></div>
<script src=”moz-extension://4a78abbc-ddec-483a-b8ba-938c0dd89fda/web/libs/ciuvo-addon-sdk.min.js” async=””></script>

I checked with iTheme Security everthing but no Maleware is found. These code look like an adveristment maleware. Any idea how i can remove it or what exactly it is?