Related blog post:
http://www.grassroots-oracle.com/2019/01/apex-authentication-switch-in-session.html
This home page is public, and the default authentication scheme is open-door credentials.
These two links allow toggling between authentication schemes at runtime, and will always force authentication.
f?p=100567:2:0:APEX_AUTHENTICATION=apex
f?p=100567:2:0:APEX_AUTHENTICATION=open
Clicking 'Secured Page' in the menu will open page 2, forcing default authentication, if not already done so.