I am using twentyfifteen theme. And all plugins are disabled. When I am trying to insert any image in the content of any page , the add media opens the popup, I choose the image, and click on the button, "insert into page". It just close the popup.And nothing happens.
I have check in the browser console. It fires a admin-ajax with the action "send-attachment-to-editor" .And all other parameters are correct for the POST params.
But it response is a html of the site home page. When in other case, where this features work, I have found that a json response is returned. I can't even point where is the problem, becuase I used the default twentyfifteen theme and my wordpress version is 4.2.2 . And no plugin is installed.