The evasi0n 1.5 jailbreak tool for iOS 6.1.2 reached the web only a couple of days ago but, as far as the evad3rs are concerned, this could be one of their latest applications designed to unlock iOS devices.
iOS 6.1.3 is very likely to patch one of the five exploits the evasi0n application is using to jailbreak iPhones and iPads, a researcher involved in the project told Forbes, so the tool could be blocked with the next iOS release.
“If one of the vulnerabilities doesn't work, evasi0n doesn't work. We could replace that part with a different vulnerability, but [Apple] will probably fix most if not all of the bugs we've used when 6.1.3 comes out,” David Wang was quoted as saying.
The only way to keep using a jailbroken iDevice is to skip the update to iOS 6.1.3. At least until the evad3rs or some other iOS hackers manage to develop a new jailbreaking solution.