When the freezer in a top-mount refrigerator defrosts, water drains down through a defrost tube into a drain pan and eventually evaporates. If the defrost drain tube is clogged with ice or gunk, the water can't drain down the tube. Instead, it collects in a puddle under the crisper drawers. Clearing the drain tube usually fixes the problem. Replace the drain tube if it's damaged or you can't clear a clog.
Water leaking from the water dispenser system can also wind up under the crisper drawers, so check water system tubing for leaks and replace any damaged tubes.