As reported by the Stay Smart Online Security Service, users should be cautious about password prompts that appear on Apple iPhones or iPads running on IOS 8.
The Mail application has a vulnerability reported that allows an attacker to create their own password prompt, it appears upon receiving an email. The Apple password prompt appears to be legitimate and could be a way for a scammer to obtain your iCloud or email login details.
This video has more details of this vulnerability.
Apple is understood to be working on a fix for the problem.