I have a situation, anyone's advice is highly appreciated. I have an external .net page which I want to iframe in my VF page, but it learnt that salesforce no longer supports Iframe. I shouldn't open that page in an popup or new window, as I will be getting some values from the .net page which I need to capture and use them. Attached is the pic
try delivering the .net page under a secure HTTPS connection. Mixed content is blocked by default in most modern browsers.
You want to iframe an external link inside VF page within Salesforce unfortunately, this might not work properly because if your organization displays non-setup Salesforce pages within a frame or , it’s possible that the pages will either display as a blank page or without the frame after clickjack protection is enabled. The behavior varies depending on your browser and its version. Although there are reasons to frame pages, framed pages can be used by hackers.
You can refer to the following documents for more details: