User armatav noticed this on another thread (https://news.ycombinator.com/item?id=25554162).
I was curious to see what would be needed to reproduce it. The issue is caused by the "glow" animation behind the todo list on the original page.
https://codepen.io/maybevain/full/mdrpPEg
There does not seem to be any lasting damage other than a reset to the lock screen, but try at your own peril.
For the lazy: https://codepen.io/maybevain/full/mdrpPEg
If nothing happens, zoom in and out quickly repeatedly.
Yes, this will respring or shut down your iPhone.