Apple released an update for Find My iPhone app that’s intended only for developers. The problem occurs where regular users can perform the update as well. However, many have noted that they cannot log-in to the updated Find My iPhone app without having a developer account.
The redesigned app icon, which was first introduced in iCloud.com beta page, does suggest that this build is intended for iOS 7 beta testers. Until Apple fix this, non-developers should avoid updating the app.
While, Find My Friends also receive a an update for bug fix, it does not appear to have any design changes and the app is functioning properly.