How to disable “ActiveX Control May Be Unsafe” popup

Your code isn't the problem. When you create the "WScript.Shell" object, IE asks that control if it is safe for scripting. The object returns "No". That's why your code doesn't work. As long as you use "WScript.Shell" you will have the problem.

One way around this is to create your own ActiveX control that is marked as "safe for scripting", but then you would have to get all of your users to install it.

Seems the original issue had nothing to do with the signature of the file, but in the implementation of IObjectSafety. For IE to allow it to be loaded, I needed to properly implement that interface, and it worked fine (even without a valid signature).

Simple example:

[ComImport()]
[Guid("CB5BDC81-93C1-11CF-8F20-00805F2CD064")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IObjectSafety
{
    [PreserveSig()]
    int GetInterfaceSafetyOptions(ref Guid riid, out int pdwSupportedOptions, out int pdwEnabledOptions);

    [PreserveSig()]
    int SetInterfaceSafetyOptions(ref Guid riid, int dwOptionSetMask, int dwEnabledOptions);
}

And the class itself:

[ProgId("Testing.Test")]
[ClassInterface(ClassInterfaceType.AutoDispatch)]
[ComVisible(true)]
public sealed class Test : IObjectSafety
{
    #region Saftey Interface
    private const int INTERFACESAFE_FOR_UNTRUSTED_CALLER = 0x00000001;
    private const int INTERFACESAFE_FOR_UNTRUSTED_DATA = 0x00000002;
    private const int S_OK = 0;

    [ComVisible(true)]
    public int GetInterfaceSafetyOptions(ref Guid riid, out int pdwSupportedOptions, out int pdwEnabledOptions)
    {
        pdwSupportedOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER | INTERFACESAFE_FOR_UNTRUSTED_DATA;
        pdwEnabledOptions = INTERFACESAFE_FOR_UNTRUSTED_CALLER | INTERFACESAFE_FOR_UNTRUSTED_DATA;
        return S_OK;
    }

    [ComVisible(true)]
    public int SetInterfaceSafetyOptions(ref Guid riid, int dwOptionSetMask, int dwEnabledOptions)
    {
        return S_OK;
    }
    #endregion

    [ComVisible(true)]
    public string TestString
    {
        get
        {
            return 'A Test';
        }
    }
}