There is an exploit that can hit only those that know how to use linux to manage their site. Apparently linux editors store a backup copy of the file being edited in the same directory of the file. Therefor when a config file is being edited a copy of it is created, and since the names the editor gives to the backup files is predictable, and usually accessible as plain text from the web, all the data in the config is exposed at edit time. It is even worse if the editor failed to erase the backup after editing was finished.
Therefor you either should not edit config files locally, but transfer them over FTP, or put then in an inaccessible location (If wordpress is installed at the root directory you can put the config file at the usually inaccessible directory above it) or replace the config script with a script that read the config, or the secret parts of it from other location.