The SeeShell Browser can not catch this dialog yet, but the solution is to use SeeShell Desktop Automation. Since it operates on the complete Windows desktop, it can see and automatically fill out this dialog. You can actually do the complete automation in SeeShellDesktop Automation.
With the scripting API, you can even combine SeeShell and SeeShell Browser. That makes sense, since the browser is still better suited for web automation since it has functions like scroll, proxy, clear cookies,… . Here is some VBS code for it. It firsts fill out the login dialog and continues in the browser.
set objDesk = CreateObject ("SeeShell")
set objWeb = CreateObject ("SeeShell.Browser")
i = objWeb.open(true)
i = objDesk.open(false)
i = objDesk.play("Fillout_Oauth_Popup")
i = objWeb.play("Continue_in_Facebook")
For others reading this, this is the kind of dialog discussed here:
