Demo

What to do:

1. Save the page to your local hard drive. [Save page as...]
2. Open the saved file in a text editor.
3. Search for one of the available select options and modify the value attribute to some random string value. Preferably to a value already used.
4. Save the file
5. Open the local file into your web browser
6. Select in the dropdown box the option that you modified the value for, and submit the form.