Nintendo recently released a fairly major system update for the Switch just recently, but now another update has swooped onto the scene. This update isn’t nearly as big as the other one; the patch notes only describe it as being another enigmatic “stability patch”.
Small, incremental such as this one have been known to be issued in order to combat piracy and hacking, though they do sometimes include minor fixes that were missed beforehand. Considering the speed at which this mini patch was released, the situation really could be either of those two. Regardless, not updating will result in the Switch trying to get you to do so anyway, so check it out in the System Settings menu as soon as possible.