Upgrade to TW8.3; HTML widget won't works

Hello, I've just made an upgrade from TW8.1 -> TW8.3 but I'm having a issue:

I have a mashup in which I only use a HTML widget in order to load a html page I created.

The problem is this widget will ignore all CSS and Javascript.

Indeed, if my result is something like

var html = "";
html += "<style>";
html += " .myClass{";
html +=" background:green;";
html +=" color:red;";
html += " }";
html += "</style>";
html += "<div class = 'myClass'>This is my text </div>";

result = html;

the <style> tag isn't read (same for script).

Do you know I can I solve this?