Modern ovens have holes in the back for things like thermostats and ignitors. Yes, you should be concerned. Not so much about the steam but it does indicate you have some sort of hole in the back of the oven or it's not properly vented. The holes for thermostats and ignitors (gas ovens) should be filled in with insulation so normally there shouldn't be a lot of venting from the back of the oven.
The bigger concern is flame potentially coming out the back, especially with broiling or convection.
The steam itself is only going to come from whatever you're cooking. Obviously there's no plumbing associated with an oven.
The back panel should be hot just by being close to the oven. Water should not be condensing on it.
I make bread and I will often throw literally big ladles full of water into the hot oven. I have to be careful not to burn my face off from the steam but I don't see any water condensation outside the oven. My bigger problem is shattering the glass in the oven door or the glass lenses oven the oven light bulbs if I accidentally splash water on the glass.