MSXML 4.0 Service Pack 2 (SP2) is a complete replacement of MSXML 4.0 and MSXML 4.0 Service Pack 1 (SP1). MSXML 4.0 SP2 provides a number of security and bug fixes. MSXML 4.0 SP2 does not replace MSXML 3.0. A security issue has been identified in Microsoft XML Core Services (MSXML) that could allow an attacker to compromise your Windows-based system and gain control over it. You can help protect your computer by installing this update from Microsoft. After you install this item, you may have to restart your computer. Once you have installed this item, it cannot be removed.