https://wccftech.com/get-your-hopes-up-saurik-is-working-on-cydia-for-ios-11-jailbreak/

In case you needed assurance that there might be an iOS 11 jailbreak, we have some good news from the creator of Cydia himself, Saurik (aka Jay Freeman).

The news regarding an iOS 11.2 / iOS 11.2.1 jailbreak was left in tatters when everyone realized that the jailbreak would never ever be released to the public, and instead would be available for developers for research purposes only. Long story short: there will never be a jailbreak for iOS 11.2 / iOS 11.2.1. But, Google’s Ian Beer went ahead and highlighted an exploit necessary for an iOS 11.1.2 jailbreak instead, which turned out to be unlucky for everyone as Apple stopped signing the firmware altogether. This means that you cannot downgrade or upgrade to that particular version of iOS no matter what you did. All hope seems lost now, does it? Wrong.