Logged wife off of her iPad and logged in as myself on this device. When I went to my iPhone, all of her passwords had transferred onto my phone (had to go through and manually delete all of them). In my eyes, this is a serious security issue as if someone could unlock your iPhone/iPad, all they would have to do is log you out and login under a different Apple ID and now have all your saved usernames and passwords.
iPhone 7 Plus
The security issue is swapping devices with somebody and not completely erasing them first. Also Apple asks if you want to keep data on the device when you sign out. If you say yes then it does that and merges the data with the next account to sign in. From there it goes into iCloud and then onto all your devices using iCloud.
I think you have to know the old user's password in order to be able to sign out. If they know that then you have much bigger account security concerns.
Make sure nobody can unlock your iPhone/iPad.
The security issue is swapping devices with somebody and not completely erasing them first. Also Apple asks if you want to keep data on the device when you sign out. If you say yes then it does that and merges the data with the next account to sign in. From there it goes into iCloud and then onto all your devices using iCloud.
I think you have to know the old user's password in order to be able to sign out. If they know that then you have much bigger account security concerns.
Make sure nobody can unlock your iPhone/iPad.
Frankly all I have ever done is sign into erased devices and then kept them until they stopped working. Apple has various ways to prevent somebody from getting into the first screen, including passcode, Touch ID and face ID. And then to dissuade thieves further you should enable SDP. That gives you a time window before anybody (even you) can get access to certain features even if the person steals a device while it is awake (such as grabbing it out of your hands while you are using it). During that time window you can set lost mode on the device so when SDP shuts down the thief is still locked out of the account because you told it to erase.
About Stolen Device Protection for iPhone - Apple Support
No, it didn’t require a password to sign out, all I did was select sign out then signed in as me. Wasn’t until a few days later when I went to sign into something on my phone that I saw all the passwords. Just scary thinking if someone could steal and hack into the 1st screen, how much information they can get by signing in as themselves.
Automatic password transfer between devices
