As always, do not update your 3ds unless you confirm your flashcart will be still working after the update.
Just as the title says, today 3ds new firimware V4.3.0-10 has released. And it has been confirmed that this new 3ds firmware blocked flashcart again, currently R4i gold from r4ids. can work on it, dstwo has released the update patch, acekard 2i was blocked again. Details below.
Cards still working on the 3DS V4.3.0-10
R4i gold 3ds (should be from r4i ds.cn, this one: R4i Gold 3DS Wood R4i 3DS flashcard For DS DSi 3DS -dsflashcart.com)
Supercard dstwo (has released the update patch, you need to update your DStwo with a DS Lite console.)
Ace3ds plus (A very new flashcart, see post here: http://www.wiihacks.com/ds-dsl-dsi-3...e-v1-50-a.html )
R4i sdhc 3ds (r4i-sdhc.com)
Do yourself a favor, don't buy crappy flashcarts.