A very real and dangerous hack was recently discovered on iOS devices which includes iPhones and iPads. It’s called XcodeGhost. In short, over 50 apps were released through the App Store that can and do steal your information, including passwords.
What can I do about the iOS Hack?
Review this list of known compromised applications. If you have any of them installed, immediately uninstall them. Next reset your password on iCloud. I would also recommend resetting passwords to any services your phone uses such as your online banking applications, DropBox, Google Drive, Amazon, eBay, etc…
If you want more information about how the compromise occurred, MacRumors has a good description here.