A crash is seen on iOS when using Vuforia 7.0 in the Unity 2017.4 LTS version (2017.4.5 and later) when using Metal graphics API and Autorotation. There is a work around available. Disabling the "Multithreaded Rendering" option in Player Settings will prevent this crash from occurring.
This issue is not present in more recent versions of Unity and Vuforia. Unity 2018.1+ and Vuforia 7.1+ do not encounter this issue and can be used without the workaround.
We are currently investigating a possible fix for the LTS version, but in the meantime please utilize one of the above mentioned workarounds.
Vuforia Engine Support.