When an untrusted applet or application displays a window, the Java Runtime Environment includes a warning banner inside the window to indicate that the applet or application is untrusted. A defect in the Java Runtime Environment may allow an untrusted applet or application that is downloaded from a malicious website to display a window that exceeds the size of a user's screen so that the warning banner is not visible to the user.

Sun acknowledges with thanks, Giorgio Maone from InformAction for bringing this issue to our attention.