Event 1041 - UIPI Extension Blocked

  • Logged Message
  • What Is It?
  • When Is This Event Logged?
  • Example
  • Remediation
  • Related topics

Logged Message

User Interface Privilege Isolation (UIPI) Extension blocking prevents loading some Windows Internet Explorer extensions that are known to be incompatible with Windows Vista, or have potential security issues. For example, this blocking prevents the Microsoft PowerPoint handler from starting without explicit user interaction.

What Is It?

UIPI blocks lower-integrity processes from accessing higher-integrity processes. For example, a lower-integrity process cannot send window messages or hook or attach to higher priority processes. UIPI in this scenario blocks extensions that are incompatible with Windows Vista as well as extensions that could pose a security risk. Extensions that could be blocked are:

  • Microsoft ActiveX Control
  • Toolbar
  • Browser Helper Object
  • Browser Extension
  • MIME Handler
  • Pluggable Protocol

A list of known extensions is listed in the registry:

HKEY_LOCAL_MACHINE (or HKEY_CURRENT_USER)\SOFTWARE\Microsoft\Internet Explorer\Extension Compatibility

When Is This Event Logged?

This event is logged when an Internet Explorer Extension is encountered that is not Windows Vista compatible or has potential security implications.


Perform the following steps to see this event logged in the Internet Explorer Compatibility Test Tool:

Note This example requires Microsoft Office Word 2003 or later and Windows Vista or later.

  1. Create a new document with Microsoft Word, and add some placeholder text.

  2. Save the document in the root directory of the local Web server as an Rich Text Format (RTF) file. For example call it test.rtf. On a Microsoft Internet Information Services (IIS) server this means putting the files in this directory:


  3. Start the Internet Explorer Compatibility Test Tool and enable logging.

  4. Start Internet Explorer.

  5. Internet Explorer needs to have Protected Mode enabled. Select the Tools > Internet Options menu item. Select the Security tab. Select the Local intranet zone and ensure Enable Protected Mode is checked. Click OK.

  6. Browse to the file:


  7. When prompted, open the file.

This will cause the UIPI Extension Block event to occur.


There is no workaround. You should be aware of this issue and design your site accordingly.

Internet Explorer Application Compatibility

Events 1040 through 1049