Safari shows "non-secure form" when authenticating by Microsoft Azure Identity

Question

I've cloned the ms-graph-training repo to test the Microsoft Graph API. I've changed the credential flow using interactive browser credential. The code looks like that:

credential = new InteractiveBrowserCredentialBuilder()
                .clientId(clientId)
                .tenantId(tenantId)
                .redirectUrl("http://localhost:4242")
                .tokenCachePersistenceOptions(new TokenCachePersistenceOptions())
                .build();

_userClient = new GraphServiceClient(credential, graphUserScopes);

Everything works fine. I can authenticate and call the Microsoft Graph API. There is just one thing that bugs me. The browser automatically opens the login page of Microsoft. After that, a popup is displayed (I am using Safari), which says that the form is not secure. Here is a screenshot:

After a click on the send button, everything works as expected. Changing to https, does not work, because the library will throw an error. Changing the Browser to Chrome will remove the popup, but the address bar says it is an insecure website. Does anybody know how to get rid of this?

Thanks a lot.