Critical Problems: * WordPress core file modified: wp-includes

I received an alert email a short time ago, and looked in my dashboard for this message about multiple wp-includes files: “This WordPress core file has been modified and differs from the original file distributed with this version of WordPress.” In the server I do see these files were accessed today one minute before I received the email. However, I was, at that time, in WordPress.com/plugins checking for updates on my sites, this particular site was one that I checked for updates.

However when I click on “See how the file has changed” none of the files have any changes made to them, according to Wordfence: “There are no differences between the original file and the file in the repository.”

I’ve scanned through a few of the files and, while I am not an expert in php, the files appear to be benign and routine.

I’m reluctant to start clicking on “fix this” if there isn’t anything wrong. Can anyone explain this apparent discontinuity?
Thank you, Matoca