Here you go the tutorial:
https://www.waikey.com/vps-tutorials/remove-js-donatelloflowfirstly-ga/
Plus Update
Depends on research, there are 3 opinion on this backdoor
1: Backdoor comes with the nulled themes or plugins, so just delete them and only use the official version.
2: The “Ultimate Addons for Elementor” plugin been hacked. Then just delete the plugin or update it if available.
3: Strange thing I met is that I have no “Ultimate Addons for Elementor” installed on my site. But my theme is based on “Option Framework”, don’t know if it’s been hacked since this framwork has not been updated for several years.
