Why some plugins files are changing?

I use the wordfence security plugin with cloudflare. Some days when this plugin scans the site, it shows some plugins one or two files have been changed. I face this issue more than one month. But still there’s no any malware or hacking issue.

If I view the actual file with the modified file, there’s a small change. This issue I face my two WordPress sites which hosted on same VPS. However, there’s no any code injection, sometimes it’s only changes of that file text. For an example, this file.

Original and modified file: – http://goo.gl/6hJdTU

I use Google 2nd verification plugin, also I setup automatically send emails when someone logged into my site.

Is it some sort of hacking?