MySQL: World-writable config warning during startup

[Alex SZAKALY]

I see a warning message during startup of MySQL (db_server):

mysqld: [Warning] World-writable config file '/etc/mysql/conf.d/trillian.cnf' is ignored.

The expected permission shall be 644 based on the default directory content:

/etc/mysql/conf.d# stat -c "%a %n" *
644 docker.cnf
644 mysql.cnf
644 mysqldump.cnf