Ticket #34064: 34064.diff

src/wp-admin/includes/file.php

@@ -318 +318 @@
                         $file['name'] = $proper_filename;
                 }
                 if ( ( ! $type || !$ext ) && ! current_user_can( 'unfiltered_upload' ) ) {
-                        return call_user_func( $upload_error_handler, $file, __( 'Sorry, this file type is not permitted for security reasons.' ) );
+                                /**
+                                 * Filter the error type when a disallowed file type upload has been attempted.
+                                 *
+                                 * @since 4.4.0
+                                 *
+                                 * @param string $var Default error message: "Sorry, this file type is not permitted for security reasons."
+                                 */
+                        return call_user_func( $upload_error_handler, $file, apply_filters( 'upload_filetype_error', __( 'Sorry, this file type is not permitted for security reasons.' ) ) );
                 }
                 if ( ! $type ) {
                         $type = $file['type'];