Before we get ahead of ourselves, there isn't any evidence to suggest this is a widespread epidemic of any sort. So far we know of exactly two reports, both of which appear on Microsoft's Xbox forums. One of the two users uploaded pics of the milky white residue that was left behind after the liquid dried up.
The user said the stains aren't causing any problems in terms of functionality. Another user on the same forum said he too saw the residue appear on his Xbox One Day One edition console, but that it eventually "just kind of dried up and went on its way."
CynicalAnarchy claims he contacted Microsoft about the issue but hasn't posted any details about that conversation. Some have questioned whether or not his claims are real or fabricated, pointing out that the liquid stains appear on top of the console, which might suggest something was spilled. Others contend that liquid could have been blown out through the top vents from the exhaust fans.
Either way, we'll keep our eye on this one to see what develops.