Unclear content is generated at the end of the page, in opencart?

Question

CMS

Hello! Such a task is to generate content at the very end of the page, after the "footer" block, which comes last. Moreover, after the footer, a block of the title /title body body format is generated. like a frame of some kind. It links to the site - https://www.namebright.com , plus incomprehensible styles appear in this block, which change the logo to your own logo. How to remove this nonsense? Can anyone come across..

Answer 1

found eval(base64('')) in the system/library/response.php
file Replaced the file with the original one from the installer and the malicious one disappeared

Answer 2

Turn on Notepad++ or another program that can search for data in files, click Find in Files and try to find this domain, or another piece of code that is inserted.