Index: wp-admin/includes/file.php
===================================================================
--- wp-admin/includes/file.php	(revision 19625)
+++ wp-admin/includes/file.php	(working copy)
@@ -1065,8 +1065,15 @@
 
 <?php
 foreach ( (array) $extra_fields as $field ) {
-	if ( isset( $_POST[ $field ] ) )
-		echo '<input type="hidden" name="' . esc_attr( $field ) . '" value="' . esc_attr( stripslashes( $_POST[ $field ] ) ) . '" />';
+	if ( isset( $_POST[ $field ] ) ) {
+		if ( is_array( $_POST[ $field ] ) ) {
+			foreach ( $_POST[ $field ] as $array_map )
+				echo '<input type="hidden" name="' . esc_attr( $field ) . '[]" value="' . esc_attr( stripslashes_deep( $array_map ) ) . '" />';
+
+		}
+		else
+			echo '<input type="hidden" name="' . esc_attr( $field ) . '" value="' . esc_attr( stripslashes( $_POST[ $field ] ) ) . '" />';
+	}
 }
 submit_button( __( 'Proceed' ), 'button', 'upgrade' );
 ?>