Actually the problem comes from /wp-includes/js/tinymce/tiny_mce_config.php and ads supported web sites.
header(“Content-type: text/javascript; charset: UTF-8”); is required otherwise the ads supported websites will add their ads after.
So just insert “header(“Content-type: text/javascript; charset: UTF-8″);” after “@ require(‘../../../wp-config.php’);” in this file and it will do it!