Currently, Apple's latest firmware is iOS 12.3. If you accidentally update or restore, you'll find yourself on iOS 12.3. Developers have been seeded with iOS 12.4 beta.
Those interested in jailbreaking are typically advised to stay on the lowest firmware possible. The unc0ver jailbreak works on all pre-A12 devices devices up to iOS 12.1.2 whereas the chimera jailbreak also works on A12 devices.
Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.