Keyboard Delete Button not working for textbox inside object which is inside iframe

Question

I have three pages (HTML documents) as following:

1. Page1 : contains only one textbox.

2. Page2 : contains object tag which using the "data" attribute calls Page1.

3. Page3 : contains iframe tag which using the "src" attribute calls Page2.

Open Page3 in IE 10 or IE 11.

Now the issue is that the keyboard's delete button is not working inside the textbox.

By seeing the structure you can understand how complicate project I am working on and I can not change this structure without introducing a lot performance issues.

I'll appreciate if any one can tell me why this is happening in IE 10/11 and not in IE8/Chrome/Firefox?