The universal web adapter is limited to interacting with only the controls within the page itself. If you need access to the windows controls, you would need to use a C# script (using UI Automation), or you can try using a Windows Adapter and attempt to interrogate the controls that way. Keep in-mind that for Chrome at least (I have not personally tested Firefox, but I believe it works the same way) you don't need to "Start" the Chrome adapter for it to match controls. That means that you can use a Windows Adapter to launch Chrome to your desired web page, interact with the necessary controls and allow the UWA to handle the page.