The iOS 11.2.2 update includes a fix for the Spectre security vulnerability: ● Available for: iPhone 5s and later, iPad Air and later, and iPod touch 6th generation ● Description: iOS 11.2.2 includes security improvements to Safari and WebKit to mitigate the effects of Spectre (CVE-2017-5753 and CVE-2017-5715). ● We would like to acknowledge Jann Horn of Google Project Zero; and Paul Kocher in collaboration with Daniel Genkin of University of Pennsylvania and University of Maryland, Daniel Gruss of Graz University of Technology, Werner Haas of Cyberus Technology, Mike Hamburg of Rambus (Cryptography Research Division), Moritz Lipp of Graz University of Technology, Stefan Mangard of Graz University of Technology, Thomas Prescher of Cyberus Technology, Michael Schwarz of Graz University of Technology, and Yuval Yarom of University of Adelaide and Data61 for their assistance.
Apple has NEVER released an update to block any jailbreak. It simply wouldn't be worth their time. They have, however, released many updates to patch security holes that the jailbreak community, by their very nature, have widely broadcast to the world. In essence, the jailbreak community has forced Apple to fix previously obscure security bugs on many occasions. I guess it sucks to be a jailbreaker. Enjoy your security bug-ridden iOS. I will likewise enjoy my less security bug-ridden iOS.