Feed attempts to import login screen

I am attempting to import a page via HTTP fetcher and XPATH parser. The page that I want to import is at http://www.example.com/app/report.php?location=1234. The login page is at http://www.example.com/app/login.php. However, the actual login is processed by http://www.example.com/app/loginAssist.php.

If I append the login variables to loginAssist.php, I log in just fine (using a browser).

I've set the authentication format to Plain (&URL=Vars). I don't know if the site uses 2-step authentication, but I've played around with that on and off.

On the import, I enter http://www.example.com/app/report.php?location=1234 as the URL. However, when debugging, I see that it attempts to import the content of the main login page (http://www.example.com/app/login.php).

I feel like I'm probably just missing something, so am hoping someone can help me configure this. Thanks!