The latest update to the 3DS firmware is listed by Nintendo as a "stability" patch.
Nintendo has released an update to the 3DS firmware that, among other "stability" fixes, corrects the Ridge Racer 3D freezing bug that they introduced in the eShop update last Monday.The newest version, 2.1.0, also includes unspecified "minor adjustments to enhance user experience."
3DS systems set up to prompt for updates automatically will be notified via a SpotPass alert. If the 3DS is not setup for these alerts the update option is available in the 3DS system settings menu.