Step 1: Login to your cPanel.
Step 2: Under the File section, click the File Manager. If the File Manager Directory Selection window comes up, click Web Root, and click the Go Button.
Step 3: Navigate to the configure.php file specified in the error. In my tests it is: /home/userna99/public_html/includes/configure.php
Step 4: Right-click the configure.php file, and click Change Permissions.
Step 5: In the change permissions window, change them to 4-4-4, then click the Change Permissions button.
Step 6: Now login to the osCommerce Admin section, and you will see the "Security risk" message is gone, and has been replaced by "This is a properly configured installation of osCommerce Online Merchant!"