Currently, Apple's latest firmware is iOS 13.5. If you accidentally update or restore, you'll find yourself on that version.
Those interested in jailbreaking are typically advised to stay on the lowest firmware possible; however, the checkra1n jailbreak makes it possible to permanently jailbreak devices between the iPhone 5s and iPhone X on any firmware version above iOS 12.3 and the unc0ver jailbreak now supports iOS 13.5 on all devices!
Source:iClarified