To fix a spout leaking on the WMF-DM-4H-SP-NB, please follow the instructions below.
1) Remove the cap from the back of the faucet by unscrewing it with your fingers.
2) Removing the cap will reveal a small, Phillips head screw.
3) Use a Phillips head screwdriver to tighten this screw.
4) Reattach the finial to the back of the faucet and screw it in.