This clip from the hit series Silicon Valley should help remind us to be a bit more careful with how we store our passwords. The post-it note is not a substitute for a password manager. We strongly recommend these password managers: 1Password (great integration with Apple products), RoboForm, LastPass, and Keypass.
A bug in iOS (the operating system for iPhone, iPod, and iPad) allows an attacker to create a genuine looking, but malicious, message requesting the user login to their iCloud, or other account, when the user is in the standard Mail app. Apple acknowledged it is working on a fix, but for now, either: 1) use an alternative app (like Microsoft Outlook for iOS, Yahoo Mail, or the GMail app from Google) for accessing your email, or 2) close the Mail app and only respond if the message newly appears when you are not using the Mail app.
You can read more about it at 9to5mac.com.