iOS 9.2.1 Jailbreak Details
If your iPhone 5s is jailbroken, and you want to keep that jailbreak, don't update to iOS 9.2.1. At least not yet.
Jailbreak developers have teased several unreleased jailbreaks and there's a chance we see one arrive before the release of iOS 9.3.
For now though, iPhone 5s users are stuck with the one working iOS 9 jailbreak for iOS 9.0, iOS 9.0.1 and iOS 9.0.2. This is a problem because there's no way to drop back down to any of those updates.
Keep an eye out for new details. We should see some emerge soon.