The system is designed to read base64 encoded characters for the database username and password. Is it to hide the these string from prying eyes. If you're updated your username and password, you have the option of encoding it with base64 or simply using the function directly.
For an example, in the config.php file:
...
define('DB_USER', base64_encode('your_db_user'));
define('DB_PASSWORD', base64_encode('your_db_pass'));
...
It is recommended to download the latest version to get benefit from the new features and maintenance updates.