Hi, I just came across this post as I’m having the same issue.
I found it was an extension I have installed on Google Chrome. This would explain why you’re seeing it only on chrome and not safari (I’m using chrome on a Macbook Pro 2015 if that helps). The extension that was causing it for me is called ColorZilla; it’s an extension to pick colors from a webpage. But I’ve had this installed for years, and it’s only since last week that this has been a problem so I can only think that it has been updated recently.
Anyway, when I disabled ColorZilla I no longer have the issue of that JS file being requested form “filtplate.net” and Avast flagging it up.
For you it may be a different extension causing the problem. Best thing to do it go through your extensions one by one and disable them, then refresh a google search result page to see if Avast pops up.