Hey there,
The file you are referring to (svgxuse.js) is expected to be in this plugin. You can see it as part of our GitHub repository here:
https://github.com/studiopress/simple-social-icons/blob/4cd95e1c46ba24bf1d6c4894833e08ebc873e631/svgxuse.js
When doing a search for “JS:Agent-EIY” and “svgxuse” together, the only result I find is your post here on the www.ads-software.com forums.
While not definitive, the lack of search results indicates these 2 things may not likely be linked in any form of attack.
https://duckduckgo.com/?q=%22JS%3AAgent-EIY%22+%22svgxuse%22&atb=v312-7__&ia=web
That being said, if you are seeing JS:Agent-EIY somewhere on your site, it would seem likely that you were infected with a trojan. See: https://www.fortiguard.com/encyclopedia/virus/7002682
But I do not see any specific evidence that the cause of this was this plugin, nor svgxuse.js
However, if you have any evidence to the contrary, please reach out to us by emailing (nathan.rice at wpengine.com) and we will be happy to work with you on resolving it.