You might have tried the Developer Tools (press F12) to find the secret script's source code, but had no luck with that. Also typing about:NewTabPageScripts.js in the addressbar didn't made you jump up from your chair, screaming some euphoric words to be remembered by your offspring...
Be sure to (temporarily) allow pop-ups!
When you look at the address bar of the newly opened tab/window, you'll find the following url: res://ieframe.dll/NewTabPageScripts.js
The res://ieframe.dll/ points to the "HTML" resource folder in ieframe.dll (located in your system32 folder). It's a resource dll with a lot (maybe all) of the about: pages. Use a resource viewer to look at all the bitmaps, HTMLs, scripts, GIFs, PNGs, AVIs, icons, dialogs, menus, strings and binaries.If you have Visual Studio, just drop the ieframe.dll on the main window. A new page opens showing you all the resources.
The New Tab page itself, is also located in the resource dll: res://ieframe.dll/TabsWelcome.htm
Just showing it in plain sight...
The opinions expressed herein are my own personal opinions and do not represent
my employer's view in any way.