any standard tests to prevent hacking?

my question may sound weird. I am useing selenium to test an application, yesterday one of my colleagues found this issue that if someone enters this:

<script type="text/javascript"> alert("This is an example of what will happen"); </script>

in a text-box where they are supposed to enter their names it will cause some problems, it's kinda like hacking!!! how can I figure out the same issues? should I be a hacker or there are some standard tests for websites(or applications) to check this kind of problems, especially for log in part?