A huge number of Web sites are employing a little-known tracking mechanism to gather information on visitors and are failing to disclose the practice in their privacy policies. The technique employs cookies generated by the Adobe Flash software and the cookies often have the same value as HTTP cookies, the researchers report. Some sites employing the Flash cookie technique include federal government sites, the authors found. Whitehouse.gov uses Flash to track visitors, and though the site discloses the use of tracking in its privacy policy, it does not mention Flash as the technology.
Source: https://threatpost.com/many-sites-using-flash-cookies-silently-track-users-081709/72964/