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.
Javascript Validation Bypass: Set the page to at least security level 1 to activate the javascript validation. Javascript validation can always be bypassed. Use a client-proxy like Burp-Suite to capture the request after it has left the browser. You can alter the request at that time. Also, Javascript can be disabled.
Method Tampering: Because the page does not specify that the input parameters must be posted, it is possible to submit input parameters via a post or a get. This is a second order vulnerability allowing other vulnerabilities to be exploited easier.
Client-side Security Control Bypass: This page attempts to implement security using client-side security controls. Any page using such controls, including this page, is vulnerable to security control bypass.
Reflected Cross-Site Scripting: This page is vulnerable to reflected cross-site scripting because the input is not encoded prior to be used as output. Determine which input field contributes output here and inject scripts. Try to redirect the user to the capture-data.php page which records cookies and other parameters. Visit the captured-data.php page to view captured data.