Open the browser with this page: https://github.com
Next step is to open the Developer Tools console
If you use Opera then you can use this keys: Ctr+Shift +C .
If you use Firefox or Chrome browsers use F12 key.
Paste the following code into the console
area to create a new inline script and add this java script:
var test = document.createElement('script');
test.innerText = 'alert("hi there");'
For example, this is a good security result on my Opera browser.
The result of this message tell us about the script we tried to execute was stopped by the browser.