https://www.theguardian.com/technology/2018/feb/15/white-ring-marks-apple-homepod-smart-speaker

White rings formed due to oils and polish in the wood reacting negatively with the silicone foot on the bottom of £319 speaker

Early adopters of Apple’s new £319 HomePod smart speaker have started complaining that the “new sound of home” is leaving white ring marks on wooden surfaces that are difficult to remove.