Hm, I’m not entirely sure that’s what’s happening here. I just tried, and it definitely returned it as application/json. I’m still not sure that’s the “correct” way to return the value, but I don’t think it would cause any issues. Can you vi the file on your filesystem and verify the contents outside of how the web server sees it?
# curl -vvvv http://siecons.com/.well-known/acme-challenge/coUifFJYKNhxO01DLoZjeeFNn8t32vqbOA3tU44PA8Q
* About to connect() to siecons.com port 80 (#0)
* Trying 181.88.192.100... connected
* Connected to siecons.com (181.88.192.100) port 80 (#0)
> GET /.well-known/acme-challenge/coUifFJYKNhxO01DLoZjeeFNn8t32vqbOA3tU44PA8Q HTTP/1.1
> User-Agent: curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.27.1 zlib/1.2.3 libidn/1.18 libssh2/1.4.2
> Host: siecons.com
> Accept: */*
>
< HTTP/1.1 200 OK
< Server: nginx
< Date: Tue, 13 Nov 2018 15:08:26 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 44
< Connection: keep-alive
< Access-Control-Allow-Credentials: true
< Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
< X-Proxy-Cache: MISS
<
* Connection #0 to host siecons.com left intact
* Closing connection #0
coUifFJYKNhxO01DLoZjeeFNn8t32vqbOA3tU44PA8Q.