Those places, yes... but most often it's in URL parameters:
h ttp://whatever.com/function.php?variable1=stuff&variable2=stuff
You would insert it where you saw the "stuff" so it might look like:
h ttp://whatever.com/function.php?variable1=<script>alert("XSS")</script>&variable2=stuff
There are lots of other places, but that should give you an idea.
- RSnake
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