The HTML Help facility in Microsoft Windows 98, 98 Second Edition, Millennium Edition, NT 4.0, NT 4.0 Terminal Server Edition, Windows 2000, and Windows XP uses the Local Computer Security Zone when opening .chm files from the Temporary Internet Files folder, which allows remote attackers to execute arbitrary code via HTML mail that references or inserts a malicious .chm file containing shortcuts that can be executed, aka "Code Execution via Compiled HTML Help File."