Some older versions of CloudBlue Commerce may have written some cardholder data insecurely to log files or core dumps.
CloudBlue Commerce (5.0 and later) comes with a tool to find and securely delete any such data. The tool is called "sensitive_data_cleanup.pl" and can be found in the tools directory. The script can be run at any time, multiple times.
While your installation may not have any of this data, you must still run this script after upgrades from older versions to make sure your system does not have any sensitive data that is not encrypted.
Removing such data is absolutely necessary for PCI DSS compliance.