After updating to WHMCS 8.8, admins may see an Application configuration file is not writable  entry in the Activity Log at Configuration > System Logs :

Updater unable to add default database tls options to configuration file: Application configuration file is not writable

The file permissions of the configuration.php file prevented the automatic updater from adding new placeholder entries to the file.

The new entries are optional. They relate to the Encrypted Database Connections feature.

You do not need to do anything to address this issue. There is no detrimental impact if the placeholder entries are not present in the file.

You may add the placeholder entries to the configuration.php file manually:

$db_tls_ca='';
$db_tls_ca_path='';
$db_tls_cert='';
$db_tls_cipher='';
$db_tls_key='';
$db_tls_verify_cert='';

For more information, see Encrypted Database Connections.