In my Rails app I use both Rails' native form_tag method and the simple_form_for method provided by the simple_form rubygem.
Both of them are leading to the following warning in the chrome console:
Mixed Content: The page at 'https://example.com' was loaded over a secure connection, but contains a form which targets an insecure endpoint 'http://example.com'. This endpoint should be made available over a secure connection.
And indeed, the rendered HTML forms use the http protocol for their action attribute.
What is the reason for that? All my other URL's use the https protocol.