I’m getting some odd log messages for the apache module modsecurity. Essentially its xml parser is breaking when random places are sending pingbacks. The requests go to xmlrpc.php and the response headers are ok, but the body is binary. The message in the modsecurity log looks like:
Message: XML parser error: XML: Failed parsing document.
After a bit of guessing and sending messages to and fro, I can now see that it is a gziped response. So I’m not sure if it is modsecurity not realising that the response is gziped or wordpress not marking it correctly. In any case I can regularly get very similar binary strings using gzip and the usual xml response. So that’s half the mystery solved.
Most of the requests are spammers so I’m not too worried. I think it also impacts legitimate pingbacks because I’ve not had any, even from the usual automatic places.