Attackers on home.mycloud.com might attempt to trick you into installing programs that harm your browsing experience (for example, by changing your homepage or showing extra ads on sites you visit). Learn more
You likely have some program (security software, antivirus software, etc.) or browser extension/plug-in that is generating that message.
Also, see the dedicated subforum for your device, apparently a My Cloud Home. This subforum (My Cloud) deals with an entirely different device.
My Cloud Home
http://community.wd.com/c/home-cloud-storage/my-cloud-home/229
