At yesterday's WWDC keynote, Apple announced the availability of the iOS 8 beta for developers. The beta is not available to users without a developer account, but apparently, someone discovered a vulnerability in the software that allows anyone to download and install the beta.
Warning
Before you do anything, you should know that installing the iOS beta on your device is risky, especially if the iPhone you plan to install it on is your only communication device. iOS betas are extremely buggy at this early stage of development, and installing a UDID by someone who isn't a registered Apple developer can even void your device's warranty.
But let's see how. Members of iCrackUriDevice have uploaded a video to YouTube that will show you the steps you need to follow to install iOS 8 on your device.
To download iOS 8, please consult Google, as it is being released online through unofficial channels. We will not publish download links for reasons described in the disclaimer above.
Watch the video

