I had automatic updates of Firefox. When it got updated to version 96.0.1 (released 14th January 2022), the log in for localhost environment stopped working.
When I returned to version 95.0.2, the log in is working on localhost correctly.
Is there a way how to change the login process, that it would be supported by the newer versions of the browsers?
I am not sure about this exact bug fix but it can be that the browsers refuse working well without https more and more. Maybe you can try https on localhost if it helps?