What could be the reason for the left text appearing on the site with links to porn sites?

Question

Malware

Hello.
The left text appears on the site:

<style>#qxbefhp {display:none;font-size:15px;margin:22px;} .zlgoahpt, .zlgoahpt a {display:none;text-align:center;position:relative;z-index:100;color:gray;}</style><span></span><b></b><div class="zlgoahpt"><div><a href="http://my-mature.com/" target="_blank">my-mature.com</a> <a href='http://www.uhtube.cc/'>Смотреть порно на мобильном</a> Женщина с волосатой пиздой смотреть <a href='http://www.ruerovideos.me/'>здесь</a> секс видео онлайн А вот и ссылка на эту <a href="http://gurman.mobi/cat/91">рубрику с размещенным видео</a> <a href="https://dosug-ekb.com/place/vyezd-na-dom" target="_blank">девушки по вызову Екатеринбург</a></div></div>

The site is made on Bitrix. This text does not appear on the local machine. How can this text appear?

Answer 1

Let's say someone stole the access password. Now he downloads the site, parses the pages, adds links there and uploads them back.
It is also possible that the Web server program has been hacked and a plug-in has been inserted that adds such links on the fly. Or someone along the way (someone's router) adds links on the fly.