INSERT .. RETURNING bypasses the absence of SELECT privilege

create database db;

create table db.t (pk int auto_increment primary key, a int default 0);

create user foo;

grant insert on db.t to foo;

--connect (con1,localhost,foo,,)

insert into db.t () values () returning pk, a;

# Cleanup

--disconnect con1

--connection default

drop database db;

drop user foo;

MariaDB [test]> insert into db.t () values () returning pk, a;

+----+------+

| pk | a    |

+----+------+

|  1 |    0 |

+----+------+

1 row in set (0.020 sec)

MariaDB [test]> show grants;

+---------------------------------------+

| Grants for foo@%                      |

+---------------------------------------+

| GRANT USAGE ON *.* TO `foo`@`%`       |

| GRANT INSERT ON `db`.`t` TO `foo`@`%` |

+---------------------------------------+

2 rows in set (0.001 sec)

MariaDB [test]> insert into db.t () values () returning *;

ERROR 1143 (42000): SELECT command denied to user 'foo'@'localhost' for column 'pk' in table 't'

MariaDB [test]> show grants;

+---------------------------------------+

| Grants for foo@%                      |

+---------------------------------------+

| GRANT USAGE ON *.* TO `foo`@`%`       |

| GRANT DELETE ON `db`.`t` TO `foo`@`%` |

+---------------------------------------+

2 rows in set (0.001 sec)

MariaDB [test]> delete from db.t returning pk, a;

ERROR 1143 (42000): SELECT command denied to user 'foo'@'localhost' for column 'pk' in table 't'

MariaDB [test]> delete from db.t returning *;

ERROR 1143 (42000): SELECT command denied to user 'foo'@'localhost' for column 'pk' in table 't'