Malware
CHINACHOPPER
a simple code injection webshell that executes Microsoft .NET code within HTTP POST commands.
CHINACHOPPER is a Windows malware family operated by APT41, EMISSARY PANDA and others.
Background
A lightweight code-injection webshell that runs Microsoft .NET code carried inside HTTP POST requests. Through this mechanism the shell can transfer files in and out, launch applications under the web server account's privileges, enumerate directory contents, reach Active Directory and databases, and perform anything else the .NET runtime permits.
Source: Malpedia (Fraunhofer FKIE).