Problem with Avery Demo Site and WPShowPost

Hi! I encounter a problem with the pre-installed WPShowPost Plugin from the Avery Demo I am using to build my site.
I was about to change some configurations on the plugin because the post were not appearing on the category page, right at the moment I opened the configuration option of the plugin, my antivirus detected a malware.
Given that, I stared scaning all the web site files and the antivirus showed the problem was located on that plugin files.

I am sending you some screenshots of this.

I also did a complete scan of my computer and found that the Trojan was in all the backups since the first backup back in the day when I bought GP, as you can see on the picture.

I want to know what is going on. Has this happened before?