How can this iPhone be vulnerated?

the phone itself can't be unless one jail break it

but try reading

If you think your Apple ID has been compromised - Apple Support

but many people thing that odd software behavior or app bugs are virus's and people hacking them too,

if someone could hack you they would take every precaution they could to make sure you did not notice it

A non-jailbroken phone cannot be hacked. Why do think you were hacked?