HTTP HTTP POST client-body-tagger HTTP/1.1 200 OK Connection: close Content-Type: text/html X-Connection: swsclose Received your input. http Two requests to the same URL. The second one is a POST request with an offending word but it's too large to buffer and tag so it gets to pass. (XXX: Privoxy could execute the tagger based on the data that fits into the buffer) proxy -s --write-out '%{stderr}%{response_code}\n' http://%HOSTIP:%HTTPPORT/%TESTNUMBER --next -d "blafasel%repeat[20000 x padding]%" -s --write-out '%{stderr}%{response_code}\n' http://%HOSTIP:%HTTPPORT/%TESTNUMBER GET /%TESTNUMBER HTTP/1.1 Host: %HOSTIP:%HTTPPORT User-Agent: curl/%VERSION Accept: */* Connection: close POST /%TESTNUMBER HTTP/1.1 Host: %HOSTIP:%HTTPPORT User-Agent: curl/%VERSION Accept: */* Content-Length: 140008 Content-Type: application/x-www-form-urlencoded Connection: close blafasel%repeat[20000 x padding]% 200 200