You install Microsoft Silverlight in Internet Explorer 7 or later. Next, you open the Manage Add-ons feature in Internet Explorer and view the Silverlight add-on information. The publisher is listed as “(Not verified) Microsoft Corporation”.
This behavior occurs because while the installation package of Microsoft Silverlight is digitally signed, the add-on file npctrl.dll is not digitally signed. Internet Explorer checks the digital signature of the control’s binary file when it determines the publisher. If the signature is missing, the publisher information will be listed as “Not verified”.
This is a behavior by design.
The installation package of Microsoft Silverlight is digitally signed. This ensures the add-on is installed from an identified resource. For more information, please see:
Internet Explorer add-ons: frequently asked questions
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