Not sure, if I can paste an HTML fragment here.
Simple form, with a single text field & submit button.
Field attributes include
minlength=“4”
pattern="[a-zA-Z0-9-_.]{4,32}"
title="'User names are 4-32 alphanumeric chars"
On submit, with a single invalid char, such as “{”, prompts me for (irrelevant) View Saved Logins. Not submitted, nor any error displayed. Works on Chrome v109
