A quick update released alongside some larger Wii U firmware.
3DS Firmware Version 4.5.0-10U became available tonight around the same time as the Wii U's latest firmware upgrade.
According to Nintendo's website, the update further improves system stability as well as enhances the user experience. Those probing the update files have found that further blocks to DS flash cards were added, and the Nintendo Zone hotspot list was updated.
As reported earlier, the eShop is down for maintenance. After this update, it is still down. UPDATE 9:08 p.m. ET - The 3DS eShop is up now, but nothing is visibly changed.
More information on this 3DS update may be coming soon, so check back with Nintendo World Report soon. And remember, a Nintendo Direct hits tomorrow.