The data dictionary DBA_USERS_WITH_DEFPWD tells us that the users who are still using their default passwords defined in table DEFAULT_PWD$.
For example, we have some users who are still using their default password in our database.
SQL> column username format a30;
SQL> select username from dba_users_with_defpwd order by 1;
USERNAME
------------------------------
HR
IX
OE
PM
SH
Now we make a test to change HR's password to a non-default one.
SQL> alter user hr identified by Welcome1;
User altered.
SQL> select * from dba_users_with_defpwd where username = 'HR';
no rows selected
The user HR has disappeared form the list.
Using the default password or not affects the account status (ASTATUS) of the user from 16 to 0 or vice versa.