UserAgent: Mozilla/5.0 (X11; CrOS x86_64 10575.58.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36
Platform: 10575.58.0 (Official Build) stable-channel cave

Steps to reproduce the problem:
1. Launch single-app kiosk app
2. Flip the convertible Chromebook to tablet mode (or to the laptop mode and back if it was in tablet mode already)
3. Swipe up from the bottom of the screen to access shelf

What is the expected behavior?
You shouldn't be able to access anything outside the single app (hence the name :) )

What went wrong?
I can close the kiosk app, open app launcher, launch Files...

Did this work before? N/A 

Chrome version: 67.0.3396.99  Channel: stable
OS Version: 10575.58.0
Flash Version: