From 4.0.0-X up to and including 9.2.0-X are safe for ninjhax, if X is between 7 and 20.
Be careful: a new system update is coming any day now. Do not update until it has been checked. The latest version at the time of writing in USA, EUR, and JPN is 9.2.0-20, while in CHN, KOR, and TWN the latest version is 9.0.