Apple has just announced iOS 8. The new version appears to be more extensible than previous versions, and one of the new possiblities is to allow developers to develop custom keyboards, different than the system's default.
Android has had this feature for quite some time. On Android, those keyboards are known as a possible security threat, most notably by acting as a keylogger.
Does iOS 8 prevent such malicious behaviour from happening? If so, what security mechanisms are in place?