Don't copy-paste terminal commands from the web

A clever fellow explains.

You surely know this: You're looking at some website with some useful shell commands. However, those commands are long as hell and you know you're probably not gonna need them for a few years or so (so there's no need to memorize them). So, what do you do? You copy-paste them. What happens?

tl;dr: whatever Javascript put into your clipboard gets run irrespective of what you thought you were copying, and the outcomes can be exceedingly unpleasant.