Unprivileged attackers can track your system-wide mouse movements from any IE page
A security vulnerability in Internet Explorer, versions 6–10, allows your mouse cursor to be tracked anywhere on the screen, even if the Internet Explorer window is inactive, unfocused or minimised. The vulnerability is notable because it compromises the security of virtual keyboards and virtual keypads. An attacker can get access to your mouse movements simply by buying a display ad slot on any webpage you visit. This is not restricted to lowbrow porn and file-sharing sites. Through today’s ad exchanges, any site from YouTube to the New York Times is a possible attack vector. Internet Explorer’s event model populates the global Event object with some attributes relating to mouse events, even in situations where it should not. Combined with the ability to trigger events manually using the fireEvent() method, this allows JavaScript in any webpage (or in any iframe within any webpage) to poll for the position of the mouse cursor anywhere on the screen and at any time—even when the tab containing the page is not active, or when the Internet Explorer window is unfocused or minimized.