SHOW DATABASES allows users with only GRANT OPTION privilege to read all databases names

CREATE USER 'g'@'%' IDENTIFIED BY 'g';

GRANT GRANT OPTION ON *.* TO 'g'@'%'; 

create database acme;

CREATE TABLE acme.leak_test (id int, secret_data varchar(255));

--connect (a1,127.0.0.1,g,g)

--connection a1 

SHOW GRANTS FOR CURRENT_USER;

--error 1142

SELECT * FROM acme.leak_test;

SHOW DATABASES;

SELECT schema_name FROM information_schema.schemata;

--disconnect a1

--connection default

DROP USER 'g'@'%';

DROP DATABASE acme;