iOS 7 Lockscreen Bug
There is a bug with Apple's first version of iOS 7 where an attacker can bypass a device's lockscreen to gain access to email, photo, Twitter, and other data. The attack requires little technical knowledge and can be done in less than a minute. The bug has been successfully verified on a variety of iPhone and iPad devices running iOS 7.
Update: Apple released iOS 7.0.2 to correct this issue. Unfortunately, another bug was discovered which allows anyone to make calls on an iPhone using just a few swipes. It is still suggested to update to 7.0.2 while Apple is working on a fix for this latest issue. If for some reason the update cannot be applied, the following mitigation is highly suggested.
To mitigate this issue until Apple releases a fix, disable the Control Center from appearing on the lockscreen. This can be done in Settings > Control Center > Access on Lock Screen > and swipe to the let until the option is greyed out. Once Apple has released a fix and the device is updated to the latest version of iOS, this setting can be enabled again.
More information about Control Center is available on Apple's support site.