Allow upload of epub files via mime-type fix

upload-mime-types.php

@@ -27,3 +27,16 @@ add_filter( 'wp_check_filetype_and_ext', function( $types, $file, $filename, $mi
     }
     return $types;
 }, 1, 5);
+
+/* Allow upload of other MIME types.
+ *
+ * These are easier as there's no possibility of misidentification.
+ */
+function ai_mu_edit_upload_types($existing_mimes = array()) {
+    // allow .epub
+    $existing_mimes['epub'] = 'application/epub+zip';
+ 
+    return $existing_mimes;
+}
+
+add_filter('upload_mimes', 'ai_mu_edit_upload_types');