The jailbreak developer iH8sn0w has confirmed that his iPhone 4s running 7.1 is currently jailbroken, but he doesn’t “have any intentions of working on a 7.1/8 jb atm.”
News of the private jailbreaks from win0cm and iH8sn0w had generated some speculation that there might be a public 7.1 jb, but iH8sn0w’s recent comments make this very unlikely. This also comes on the heels of pod2g’s open remarks that the evad3rs are not actively working on a 7.1 jailbreak, but will likely focus their efforts on iOS 8.
Private jailbreaks are not uncommon, especially when the jailbreak involves either copyrighted code or NDAs, or if the jailbreak doesn’t meet the standards that would be required for a public release. A lot of work goes into creating a jb tool that works consistently across all devices and is simple enough for public use.