This update exists, but you won't really notice anything new.
http://www.nintendoworldreport.com/news/30879
Nintendo released a system update yesterday for the Nintendo 3DS.
The update upgrades your system to version 4.2.0-9U. According to Nintendo's website the system update adds "Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience."
Well, it's good to see that Sony's not the only company who likely masks their anti-piracy firmware under the B.S. banner of "improved stability".
It blocked several flashcarts from working. It's an anti-piracy update.