Source? I could understand (!) `reboot` (with backticks) evaluated by mistake inside a shell script; but still reboot needs high privileges.
So open up a chat app, type return, reboot, return. Tada.
I can't find some original sources, but there is a summary I found on Slashdot. https://mobile.slashdot.org/story/08/11/08/1720246/bug-in-an...