Basement Toilet Drain overflowing

[1victorianfarmhouse]

I have a toilet in the basement of my house that goes into a drain in the concrete floor. The toilet is not installed. The drain is over flowing a little bit with the plug in place as the picture shows. I recall it used to not be overflowing even with no plug in place. Is there some type of backup going on or do I just need to install the toilet and rubber gasket and tighten them down? Thanks!

 

[Eddie_T]

That happened to me when I was renting and it proved to be a septic tank backup.