What do I need to do? is my Apple ID COMPROMISED?
The first thing is to NOT click on the links in the message (if any). Then refer to this article:
If you think your Apple ID has been compromised - Apple Support
See the section:
How do I know if my Apple ID was compromised?
and especially the last link in that section:
If the message has a link, don't follow it as noted.
If it doesn't, it is likely from Apple. Go to appleid.apple.com yourself by typing in to a browser to check.
Second time getting a msg like this and changed I'd login : Dear， Your Apple ID was signed in iCloud on Alexander's iPhone. OS: iOS 9.2.1 If you believe an unauthorized person accessed your account,please sign in and manage your account immediately
