Since the release of iOS 7 beta 3 yesterday a lot of people have been wondering whether or not it patches the Evasi0n7 Jailbreak and the answer is surprisingly no. iH8Sn0w sent out a tweet confirming that beta 3 is actually still Jailbreak safe, but a later beta would likely still patch the exploits Evasi0n7 relies on.
Since everyone seems super worried… Today's iOS 7.1 beta 3 (11D5127c) does NOT patch evasi0n7. Another beta probably will though!
— iH8sn0w (@iH8sn0w) January 7, 2014
Unfortunately, however, even though Evasi0n7 still technically works on iOS 7 beta 3 it was not designed to Jailbreak that firmware specifically so you will be returned with an error if you try.
There is actually an unofficial version of Evasi0n7 though that has been circulating the interwebs that has been modified to be able to Jailbreak iOS 7 beta 3 (build 11D5127c) Untethered. So if you are a developer currently on iOS 7.1 beta 3 and would still like an Untethered Jailbreak you can download this unofficial version of Evasi0n 7 now and Jailbreak by following these instructions.
Download Unofficial Evasi0n7 for Mac
Download Unofficial Evasi0n7 for Windows
Just keep in mind these are unofficial versions and are not sanctioned by the Evad3rs, but there have been a ton of people who have had success utilizing this unofficial build of Evasi0n7 so you should have nothing to worry about.