X-Forwarded-* headers being appended about istekbin-api HOT 5 CLOSED

curl https://api.istekbin.com/r/addde30e-82ad-420f-b768-31a1c182aa0b -v
*   Trying 165.22.30.134...
* TCP_NODELAY set
* Connected to api.istekbin.com (165.22.30.134) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/cert.pem
  CApath: none
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Client hello (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS change cipher, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES256-GCM-SHA384
* ALPN, server accepted to use h2
* Server certificate:
*  subject: CN=api.istekbin.com
*  start date: May 17 20:17:21 2020 GMT
*  expire date: Aug 15 20:17:21 2020 GMT
*  subjectAltName: host "api.istekbin.com" matched cert's "api.istekbin.com"
*  issuer: C=US; O=Let's Encrypt; CN=Let's Encrypt Authority X3
*  SSL certificate verify ok.
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x7fe046805200)
> GET /r/addde30e-82ad-420f-b768-31a1c182aa0b HTTP/2
> Host: api.istekbin.com
> User-Agent: curl/7.54.0
> Accept: */*
>
* Connection state changed (MAX_CONCURRENT_STREAMS updated)!
< HTTP/2 400
< server: nginx
< date: Sat, 23 May 2020 15:20:26 GMT
< content-type: application/json; charset=UTF-8
< content-length: 53
< access-control-allow-origin:
< access-control-expose-headers: Location
< vary: Origin
<
{"message":"X-Forwarded-Proto header is forbidden."}
* Connection #0 to host api.istekbin.com left intact