The Window.open method in a WebBrowser control application returns NULL in Internet Explorer 8

Consider the following scenario:

• You have Windows Internet Explorer 8 installed on a computer that has User Account Control (UAC) enabled.
• You run an application that hosts a WebBrowser control.
• The WebBrowser control application contains a script that calls the window.open method to open a Web page in a new window.

In this scenario, the window.open method may return the NULL value. Additionally, you may receive an error message that shows that the window cannot open.

This issue occurs when the following conditions are true:

• Protected Mode is enabled in Internet Explorer 8.
• The window.open method tries to open a Web page that Internet Explorer 8 renders outside Protected Mode. Such as, a Web page that is contained in the Local intranet zone or the Trusted sites zone.

Note This issue occurs in the following operating systems:

• Windows Vista
• Windows Server 2008
• Windows 7
• Windows Server 2008 R2

This issue occurs because Internet Explorer 8 changes the default integrity level for a new browser page to the low integrity level. When you use the window.open method to open a Web page that renders at the medium integrity level, Internet Explorer 8 redirects the Web page from the initial window that has a low integrity level to a window that has the medium integrity level. Because of this redirection, the window.open method returns the NULL value.

Security update information

To resolve this problem, install the most recent cumulative security update for Windows Internet Explorer. To do this, visit the following Microsoft Web site: For more technical information about the most recent cumulative security update for Windows Internet Explorer, visit the following Microsoft Web site: Note This update was first included in security update 978207 (MS10-002). For more information, click the following article number to view the article in the Microsoft Knowledge Base:

For more information about the WebBrowser control, visit the following Microsoft Web site: