Stop using the appliance
Do not continue running a leaking dishwasher. Shut off the relevant water supply if you know how to do so safely and arrange for the appliance or plumbing fault to be corrected.
Check concealed areas
Built-in dishwashers sit next to cabinets and often over finished flooring. Water can migrate beneath these materials before it becomes visible.
Restore the wet materials
Once the leak is fixed, remaining water and moisture still need attention. Drying decisions depend on the materials affected and how far the water traveled.