MySQL can read a default database password from an environment variable called MYSQL_PWD Avoiding use of this environment variable can better safeguard the confidentiality of MySQL credentials. Using the MYSQL_PWD environment variable implies MySQL credentials are stored as clear text.
Solution
Check which users and/or scripts are setting MYSQL_PWD and change them to use a more secure method. For unattended logins you should consider - MySQL Configuration Editor - Different authentication methods (e.g., X509 certificate verification) - Use MySQL Enterprise LDAP plugin with Kerberos or SASL tokens.