How to write a fail message for login attemps from fcc

Hi,

I need a solution to write a message to the client when using a custom fcc (start from login.fcc but adding custom layout) when the user credential fail (bad user or password)

A solution using SMRETRIES or other cookies from CA SSO is not an option if we need to read it from the client side since are ACO have UseHttpOnlyCookies=true.

We are in version 12.8

Thanks