Use a utility knife to score a line about 10 inches 25 cm long into your drywall at the location where you see visible signs of a water leak mold discolored drywall etc.
Superhydrophobic wall siding leaking water.
Although vinyl is impervious to water when installed as directed by the manufacturer vinyl siding as a whole is not completely watertight.
Then using a drywall saw cut along the line you just scored.
Water leaks at soffit or eave overhang penetrations for chimneys that permits water to leak at the roof surface then pass behind the siding if the chimney is not properly flashed.
Vinyl siding installs in pieces so gaps and overlaps.
Wood siding leaks damage.
Ultimately water began to appear on the floor of the kitchen inside.
My photo above of ice below some courses of vinyl siding traces a moisture problem traced to improper installation of a through wall vent for a direct vent heating appliance.
If it is a cantilevered area as in this case place your hand at the base of the wall and feel for.