Hack with confidence.
Page html5-storage.php is vulnerable to at least the following:
HTML Injection: It is possible to inject your own HTML into this page because the input is not encoded prior to be used as output. Determine which input field contributes output here and inject HTML, CSS, and/or Javascripts in order to alter the client-side code of this page.
Document Object Model (DOM) Injection: User input is incorporated into the document object model (DOM) of the page itself. This allows a user to inject HTML which will be incorporated into the source code of the page. The browser will execute this new code immediately.
HTML 5 Web Storage Theft and Manipulation: Using a cross site scripting attack, this page is vulnerable to having an attacker read, insert, update, or delete the values stored in the HTML5 web storage.