Site Hacked – All posts and pages deleted, mystery comments left

Hi, this is the second time this same exact thing has happened to our OptimizePress site. I realize I may be asking in the wrong place and will ask the OptimizePress people the same thing. But in case anyone on here knows what I am talking about…

All the pages and posts were deleted, and mysterious comments were left at or around the same time everything was deleted. We don’t see any site visitors at the times when these comments are left. The comment author is always “1”, where the domain should be is “1” and the link is “https://1” and the comment says nothing but “1” Of course there is no avatar and the only thing you can click on is the link to https://1 which doesn’t exist.

Since everything is deleted, you get a 404 error when you try to load any pages. When you go to the home page, you then see the “OptimizePress Getting Started Guide” as if it’s a brand new installation. However you can still go the the Dashboard and all the plugins and comments are still there. 13 of the pages are still there also, but they must have been drafts or tests as they weren’t linked anywhere on the site and they have no content. 100% of the posts are gone.

We have daily backups so we’re not stressing over it, but I would like to know if anyone else has encountered this same hack. I couldn’t find anything about it anywhere online.

Thanks in advance for your insight.