It appears that today's iOS 8.1.3 update fixes many of the exploits that were used for the iOS 8 TaiG jailbreak, which worked up until iOS 8.1.2. The earlier Pangu jailbreak was disabled with the iOS 8.1.1 update that was released on November 17.
TaiG has not yet confirmed whether iOS 8.1.3 breaks its jailbreak tool, but reports on the MacRumors forums and on Twitter suggest that is indeed the case. Apple's support document detailing the security fixes in iOS 8.1.3 credits the TaiG jailbreak team for finding four now-patched vulnerabilities in the operating system.
At the current time, Apple is still signing iOS 8.1.2 so it's possible to downgrade from iOS 8.1.3 back to iOS 8.1.2 or upgrade to iOS 8.1.2 from an earlier version of iOS, but that could end at any time.
Released this morning, iOS 8.1.3 includes a range of bug fixes including a repair for a lingering Wi-Fi issue, and it also reduces the amount of storage space required to perform an iOS update.