Why does my upstairs toilet leak through the wall in basement by Vent stack, but shower does not?
If the toilet is leaking from he bottom, it is usually the wax ring. I would start by replacing it to see if that resolves the issue. You can replace the wax ring by removing the toilet yourself. The part is not that expensive. If you’re not comfortable making the repair, or if you are not sure that is the issue, then a licensed plumber can assist you with the diagnosis.