Thank you for your help. I cleaning the website this morning and the analyze inform me that there are no trace of this code. But we always find problems.
First, wordfence find 3 file and write me this message :
init.php
compat-functions.php
comment-edit.php
” This file is in a WordPress core location but is not distributed with this version of WordPress. This scan often includes files left over from a previous WordPress version, but it may also find files added by another plugin, files added by your host, or malicious files added by an attacker.”
Secondly, i find problems with images :
tinymce/skins/wordpress/images/animation_d1.gif
This file appears to be installed or modified by a hacker to perform malicious activity. If you know about this file you can choose to ignore it to exclude it from future scans.