I'm glad I looked under the kitchen sink. The large bottle of dish soap that I keep under the sink had somehow developed a cut in the plastic and had slowly been leaking soap for some time.
Fortunately, every time we move into a house, we cut linoleum to size and put it in the cabinets under the sink. This saved us for sure as the base of the cabinet would have definitely been ruined. As it was, I took a metal spatula and scooped the soap into the garbage. So glad I found it when I did. I emptied the rest of the soap into an empty water bottle.