Update using-widevine-cdm-plugin.md

Describe changes in Widevine CDM plugin based on new widevine requirements

Relates to: #12427
Relates to: #10806

docs/tutorial/testing-widevine-cdm.md

@@ -2,6 +2,21 @@
 
 In Electron you can use the Widevine CDM library shipped with Chrome browser.
 
+Widevine Content Decryption Modules (CDMs) are how streaming services protect content using HTML5 video to web browsers without relying on an NPAPI plugin like Flash or Silverlight. Widevine support is an alternative solution for streaming services that currently rely on Silverlight for playback of DRM-protected video content. It will allow websites to show DRM-protected video content in Firefox without the use of NPAPI plugins. The Widevine CDM runs in an open-source CDM sandbox providing better user security than NPAPI plugins.
+
+#### NOTE:
+As of [`Electron v1.8.0 (Chrome v59)`](https://electronjs.org/releases#1.8.1), the below steps are may only be some of the necessary steps to enable Widevine; any app on or after that version intending to use the Widevine CDM may need to be signed using a license obtained from [Widevine](https://www.widevine.com/) itself.
+
+Per [Widevine](https://www.widevine.com/):
+```
+Chrome 59 (and later) includes support for Verified Media Path (VMP). VMP provides a method to verify the authenticity of a device platform. For browser deployments, this will provide an additional signal to determine if a browser-based implementation is reliable and secure.
+
+The proxy integration guide has been updated with information about VMP and how to issue licenses.
+
+Widevine recommends our browser-based integrations (vendors and browser-based applications) add support for VMP.
+```
+To enable video playback with this new restriction, [castLabs](https://castlabs.com/open-source/downstream/) has created a [fork](https://github.com/castlabs/electron-releases) that has implemented the necessary changes to enable Widevine to be played in an Electron application if one has obtained the necessary licenses from widevine.
+
 ## Getting the library
 
 Open `chrome://components/` in Chrome browser, find `Widevine Content Decryption Module`