When an update is found, an pop-up alert can appear on the screen:
Click the pop-up to open the updated web page, right-click to close the pop-up without opening the web page.
If there appears to be many pop-up notifications, holding down the shift key while clicking will open all the queued pop-ups at once, while holding down shift when right-clicking will close all the pop-ups in the queue.
If the pop-up window is not appearing, check the Update preferences.