3DS:Is it safe to update?

The current firmware version is 11.17.0-50.

If the console already has CFW
Before the console can be updated, make sure Luma3DS is on the most recent version. To check its version, hold while turning on the console.

If an update happens on an old version
The worst that may happen if you update the system software without running a compatible version of Luma3DS is that the console may turn on to an error screen. This usually means that it could not patch the new firmware. The fix for this is to manually replace  on the SD card with a newer version of Luma3DS. See Restoring / Updating CFW on 3DS Hacks Guide for more information.

If the console does not yet have CFW
New 3DS consoles can use super-skaterhax. Old 3DS consoles can use MSET9.

Other exploits are available at 3DS:Alternate Exploits. Most of these depend on having certain games or a second console with custom firmware.

Any console on any version can be hacked with ntrboot, but this requires a compatible DS flashcart.