GECKOFX

Instalar el paquete Nuget de GeckoFX https://www.nuget.org/packages/GeckoFX/ o referenciar las dlls Geckofx-Core y Geckofx-Winforms.

En la barra de herramientas, elegir elementos ... seleccionar la dll Geckofx-Winforms.dll y ya dispondremos de GeckoWebBrowser para añadirlo al diseñador.

Sub New()

        InitializeComponent()

        Xpcom.Initialize("Firefox")

End Sub

Private Sub GeckoWebBrowser1_DocumentCompleted(sender As Object, e As Gecko.Events.GeckoDocumentCompletedEventArgs) Handles GeckoWebBrowser1.DocumentCompleted

     With GeckoWebBrowser1

         'login

         If .Document.GetElementById("idpage").GetAttribute("value") = "login" Then

             'inyectamos script para validarnos

             Dim script = .Document.CreateElement("script")

             script.TextContent = "function logon(){" & _

                 "document.getElementById('username').value = 'myuser';" & _

                 "document.getElementById('password').value = 'mypassword'" & _

                 ";document.getElementById('login_form').submit();}"

             .Document.GetElementsByTagName("head").First().AppendChild(script)

             .Navigate("javascript:void(logon())")

         End If

     End With

  End Sub