In case you missed it, evasi0n7 was updated twice today. Once to v1.0.3 to include support for iOS 7.1b3 and various fixes, and one more time just now to v1.0.4 which includes important untether security fixes for the jailbreak of iOS 7.
Existing jailbreakers will be able to install the update via Cydia as soon as Saurik refreshes his repo. If you want to jailbreak your device, download evasi0n7 v1.0.4 below and follow this tutorial
Download evasion7 v1.0.4: