I purchased 2 plug in diffusers from pier one. One did not leak and one did, all over my vanity top and ruined the finish.
Pier one said there was nothing they could do because I no longer have the diffuser. ( I got rid of it to prevent and other damage). I have pictures of the damage.
I was told there is a warning that the oil can cause surface damage, but my point is when you use something as it is designed to be used you should not have a problem. There is no warning on the diffuser itself.