"We added the X-Content-Type-Options: nosniff header to our raw URL responses way back in 2011 as a first step in combating hotlinking. This has the effect of forcing the browser to treat content in accordance with the Content-Type header. That means that when we set Content-Type: text/plain for raw views of files, the browser will refuse to treat that file as JavaScript or CSS."
https://github.com/blog/1482-heads-up-nosniff-header-support...