Oracle authorizes another user to access data objects that they have created

After Oracle is installed, there is a default Scott user who has a default EMP table, and how does the newly created user have access to the table as well?

Authorized xiaoming This user to access the EMP table, but xiaoming only SELECT permissions, if you want to give him delete permissions, only need to change the Select to delete, if you want to give him all the permissions, you can change the select to all.
So how do you revoke authorization?

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Oracle authorizes another user to access data objects that they have created