Ubuntu 18.04: clear passwords on login console TTY1

After upgrading from 14.04 -> 16.04 -> 18.04 I recognized that all the GDM login input - that means user names and passwords - is logged to the login console TTY1.

# procedure to reproduce:

* GDM login by password
* switch to TTY1 by Ctrl-Alt-F1
* user(s) + password(s) is/are visible on text console

Note: at the moment I cannot reproduce that phenomenon - because Ctrl-Alt-F1 brings me directly to the GDM login manager. Not to the TTY1 text console anymore?!?

# questions:

- Has someone else observed that phenomenon?
- How can I get to the TTY1 text console to be able to reproduce that problem?
- How to prevent passwords are logged to console?

Thank you!