Upload CSV File
WordPress Plugin Staff List CSV – Upload CSV File.
Upload CSV file to WordPress Media Library.
Sorry, this file type is not permitted for security reasons.
You may get this message when CSV file type is not supported by WordPress library.
As the message implies, WordPress default configuration limits the types of files that you can upload to your site. However, by adding a small code snippet to wp-config.php file or using a free plugin, you can manually expand the list of allowed file types.
For solution, please Google: wordpress file type is not permitted for security reasons.