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.