Eval is a notoriously controversial language feature. Douglas Crockford flat out rejects it. I'm wondering what specific risks Eval brings about. According to [this](https://stackoverflow.com/questions/86513/why-is-using-javascript-eval-function-a-bad-idea) question, `Improper use of eval opens up your code for injection attacks`.

What are some improper uses of the Eval command, and what security holes do they open up?