I am using chibi.js: https://github.com/kylebarrow/chibi/tree/master for some basic fuctionality because it is smaler than jquery.

Unfortunately the AJAX function does not seem to work anymore. I get an CORS error:

Access to XMLHttpRequest at 'https://example.com'     from origin 'https://example2.com' has been blocked by CORS policy: Request header field x-requested-with is not allowed by Access-Control-Allow-Headers in preflight response.

How can I fix the problem and update chibi.js?

When I use jQuery it works fine.