Someone else signing into their iCloud on my phone

If you leave them with your phone unattended they can access your data directly.

Keep an eye over their shoulder.

They will need their own trusted device to receive the 6 digit code for their own icloud access so the situation would be impracticable and unnecessary anyway.

Hello ~ I would be wary of doing that and as *LD150* posted “They will need their own trusted device to receive the 6 digit code for their own icloud access so the situation would be impracticable and unnecessary anyway.” thus making the whole process suspect in my opinion. Why would someone else want to do that would be my question?

~Katana-San~

if they typed in icloud.com/find they don't need a code and it doesn't give full access to their account, only to Find.

Just don't let anyone have unsupervised access to your phone.

You're welcome, and right to think about it.