php nginx server got strange header and post data from http request

Question

Our app server got some strange request, http headers like:

"Content-Type": "application/x-www-form-urlencoded",
"Content-Length": "3177",
"Host": "xxxxxxxxx",
"Accept": "*/*",
"Accept-Encoding": "gzip",
"Msisdn": "12345678",

And the http post body read using file_get_contents('php://input') was beginning with:ISDN: 12345678\r\n\r\n

The Msisdn entity header and ISDN: 12345678\r\n\r\n were not sent by out app client.

Our app written in cpp using libcurl to deal with http request. I really do not know what has happened now. Especially the ISDN: 12345678\r\n\r\n in post body content.

All suggestions are welcome.

Answer 1

Clients can add whatever headers they want, as can proxy servers. This header is added in by some mobile networks for all requests.

Detect an MSISDN (mobile number) with the browser