How do I get the html source code of a Cef3 browser in another application? (Closed source)

Job ID: 34147276

Budget: €8 – €50 EUR

Hello!
Another software uses the Cef3 browser in C#.
The other software injects javascript at each FrameLoaded event.
I want to see the source code of the html page.

But it is closed source, and I can not right-click and says "Show source html".

I need somebody who has a great fresh idea how to get the source code anyways.
I can give you access to my test machine via teamviewer or anydesk so that you can try it yourself.

If you can do, then I need the script for each page because I think some pages (depending on the URL get different javascript code).

Thank you!
Related categories: JavaScript C# Programming Chromium