Has the new toilet been fitted, or is this around the old one? If it's the old one, are you really bothered, since it'll be getting replaced....?
If it's the new one, then;
If it's condensation, you'll find it on the outside of the cistern, or on the inlet pipe which supplies the water. Most likely to be condensation if you keep the bathroom VERY warm, is this will make the relative difference between ambient air and incoming water greater.
If there's no sign of leaks from the inlet pipe, overflow pipe, and the junction where the cistern joins the pan, then shine a bright light into the bottom of the pan and look for cracks in the porcelain. If the pan is badly supported or on uneven boards, it can crack over time.
Is the carpet wet, or just the boards underneath?
Regards, Graham