To prevent opaque cache files, now all the CDN files will be requested in 'cors' mode if the cdn_cors_enabled global setting is enabled. Before enabling the setting, should enable the cors in the CDN server by adding the response header `access-control-allow-origin: *` or `access-control-allow-origin: https://discourse.example.com.`
And other external file requests other than CDN will not be cached if the response type is opaque.
This reverts commit e3de45359f.
We need to improve out strategy by adding a cache breaker with this change ... some assets on CDNs and clients may have incorrect CORS headers which can cause stuff to break.
Vinoth Kannan