A few months ago the Dev Team published a dowgrande method for iOS 5.x using redsn0w and although Apple had plenty of time to block it, it seems that they haven't done so yet. MuscleNerd confirmed today on Twitter that the solution designed by his team is still usable, expressing his surprise after leaving it active by the American company. At the moment, only terminals released before the iPad 2 tablet can downgrade to iOS 5.0.1 or 5.1 if you have SHSHs for them, but the iPad 2, iPhone 4S and iPad 3 are immune to this method.
Besides MuscleNerd's method, there is another one discovered by iH8sn0w, but this would not be known by Apple and would allow the downgrade to any version of iOS 5, for any of the iDevices sold by Apple, but only with the use of SHSH. We don't know anything about iH8sn0w's method for now, but if Apple didn't know how it was used, then it wouldn't have been able to block it. We will find out if it will be functional in the following days, but iH8sn0w said that he would like to launch it only together with iOS 6, so it is not known if we will have it available until then.
UPDATE: MuscleNerd talks about a different downgrade method than the ones discussed above.
