See https://productforums.google.com/forum/#!topic/chrome/ef3GmyyY2PM for the fun that can be had with hidden extensions.
The thread is a year old and a later update prevented extensions from hiding in the address bar, but someone may have found another avenue. Or it may be masquerading as a benign program.
The thread is a year old and a later update prevented extensions from hiding in the address bar, but someone may have found another avenue. Or it may be masquerading as a benign program.