This article covers methods to resolve WordPress error "Sorry this file type is not permitted for security reasons". Basically, "Sorry this file type is not permitted for security reasons" in WordPress occurs when we try to upload a document to the WordPress library.
As we explained above, WordPress default configuration limits the types of files that you can upload to your site for security reasons.
To Fix "Sorry, This File Type Is Not Permitted for Security Reasons" Error in WordPress, Try to Use the Free WP Extra File Types Plugin:
1. If you'd prefer not to edit your wp-config.php file and/or you want more control over exactly which file types can be uploaded to your site, you can use the free WP Extra File Types plugin at WordPress.org
2. Once you install and activate the plugin, go to Settings → Extra File Types in your WordPress dashboard.
3. There, you'll see a lengthy list of file types. Check the box next to the file type(s) that you want to be able to upload and then click Save Changes at the bottom.
4. If you don't see the file type that you'd like to upload on the list, you can also add your own custom file types at the bottom of the plugin's settings list.