The iframe was autofilled with credentials. This is a security issue - the browser's autofill should NOT fill forms inside iframes from different origins.
Main Page Login
Test Instructions
1Fill in the login form with test credentials
2Allow your browser to save the credentials
3Refresh the page and observe autofill behavior
4Verify that the iframe below does NOT get autofilled
!If the iframe gets autofilled, a red warning banner will appear