You can use SetInput, or SetAttribute function to set the value. For example, navigate to google page, then use Menu -> Design -> Test Scripting, and run this:
Code:SetInput('site', 'test');
JavaScript('alert(document.tsf.site.value )')
You can see the hidden site value has been changed.
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Also, IRobot will never trigger to go any other site except the site you are going. The vizury.com probably is trigger by the site you are visiting or you may have affected by some adware.