Charging Li-Ion 4S with TP4056 (DC isolation)
From the pictures of the circuit board that looks like it has "functional isolation", but the parts on the underside seem a little close together for me to say that it could have "safety isolation" too.  Also that greem film capacitor looks like the wrong type for its location.

So, the batteeries probably won't explode, but it might electrocute you.