JavaScript injection into HTML documents using Fiddler

JavaScript Injection

import Fiddler;

class Handlers {
    static var injectJs = "<script>alert('I see you enjoy YouTube.')</script>";
    static var hostList = new HostList("*.youtube.com");

    static function OnBeforeResponse(oSession : Session) {
        // Filter to only HTML documents and on the domains we want
        if (hostList.ContainsHost(oSession.hostname) && oSession.oResponse.headers.ExistsAndContains("Content-Type", "text/html")) {
            oSession.utilDecodeResponse();
            oSession.utilReplaceInResponse('</head>', injectJs + '</head>');
        }
    }
}