Those three pipes are fuel tank breather hose (petrol), fuel tank drain hose (petrol) and reservoir tank breather hose (coolant) and yes that is the engine oil filter immediately behind them.
Touch it, feel it and smell it - petrol, coolant or oil?
If its just one single overnight drip I very much doubt it will be petrol, engine oil or coolant. Unless its fuel or coolant that entered one of the over flow pipes by way of evaporation and condensation in which case everything is just fine and the over flow pipes are doing what over flow pipes do. Failing that its most likely to be chain fling or something flung up from the road.
Conclusion - Thoroughly clean the area up with a goodly dousing of maintenance spray such as GT85 or similar and wipe it down with an oily rag and check again, now that you know what your looking for or, do nothing more and it’ll probably not show for another week or two 
