If you have found water perhaps overflowing from the drip pan under your refrigerator, and found the drip pan full, your first instinct may to be to look for a leak. However, that is likely not your problem. The good news is a full drip pan in your refrigerator means it is working as designed in at least one way. A drip pan in a refrigerator is meant to catch any water that needs to be drained away from the inside of the refrigerator. Ideally, small amounts of water will enter the drip pan and safely evaporate away instead of becoming standing water. However, when there is too much water in the drip pan, you need to look into the cause. This problem can be caused by a few different issues.
In most cases, the water that ends up in the drip pan is from the defrost function. It melts away excess frost. If there was a large amount of frost in your freezer and the defrost suddenly started working, this can lead to a higher amount of water in the drip pan.
Another potential cause of a full drip pan is that the door gasket is faulty. This is causing condensation on the inside of your refrigerator as warm air meets cold air. Usually there is just a small amount when you open the refrigerator, but a constant stream of warm air from a faulty door seal can produce a lot of moisture that slides down to the drain tube and into the drip pan.
You will also want to check the ice chute door. If it is stuck, even just a small amount, the influx of warm air will cause melt inside your freezer. This will then drain out normally, but will still produce more water than your drip pan can handle.