HTMLObjectElement: contentWindow property
  The contentWindow read-only property of
  the HTMLObjectElement interface returns a WindowProxy
  representing the window proxy of the object element's nested browsing context, if any;
  otherwise null.
Value
A Window, or null if there are none.
Specifications
| Specification | 
|---|
| HTML Standard  # dom-object-contentwindow  | 
Browser compatibility
BCD tables only load in the browser