It’s a tale as old as time (and, perhaps, a song as old as rhyme): Apple releases a new version of iOS, hackers immediately get busy finding security vulnerabilities to exploit, eventually claw together a jailbreak, only for Apple to then find out about the flaws and fix them for the new iOS version.
Rinse and repeat.
Having released iOS 7.1, Apple has also released a list crediting the individual researchers and companies who helped spot security issues with the previous version of iOS — including jailbreak specialists Evad3rs, the team behind the iOS 6 and 7 jailbreaks.