A couple of users on the Xbox Support forums are complaining about quite an unusual issue with their Xbox Ones. Their Xbox Ones were allegedly leaking a liquid that was leaving a milky-white residue, from inside the console itself.
From all accounts, it seems that it could be the thermal compound leaking out (a heat-conducting compound that sits between a chip and its heatsink, to help channel generated heat from a graphics/CPU chip to the heatsink to dissipate), though the compound itself would have to have been applied quite liberally to leak out. Seeing as the Xbox One’s huge heatsink-fan assembly sits at the full right-front of the console, near the vents, it wouldn’t be much of a stretch for the compound to leak out if too much was accidentally applied during assembly.
More at: http://www.spawnfirst.com/news/rumor-xbox-one-leaking-liquid-two-issues-reported/