Ticket #37647: 37674.patch

 Index: wp-admin/includes/file.php
 ===================================================================
 --- /var/www/html/src/wp-admin/includes/file.php       (revision 38260)
 +++ /var/www/html/src/wp-admin/includes/file.php       (working copy)
 @@ -1260,7 +1260,7 @@
  ?>
        <p class="request-filesystem-credentials-action-buttons">
                <button class="button cancel-button" data-js-action="close" type="button"><?php _e( 'Cancel' ); ?></button>
 -              <?php submit_button( __( 'Proceed' ), 'button', 'upgrade', false ); ?>
 +              <?php submit_button( __( 'Proceed' ), 'button button-primary', 'upgrade', false ); ?>
        </p>
  </div>
  </form>