S3/Cloudfront CORS (Cross-Origin Resource Sharing) Configuration for Webfonts in Firefox. make sure to redistribute Cloudfront after applying this config to the S3 bucket. Also you should restrict the origin to you domain, just to be safe.

gistfile1.txt

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
    <CORSRule>
        <AllowedOrigin>*</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>Content-*</AllowedHeader>
        <AllowedHeader>Host</AllowedHeader>
    </CORSRule>
</CORSConfiguration>