If they've not configured nginx carefully, it will be buffering request bodies to temporary files on disk. So your data might not really be going to /dev/null

If they've not configured nginx carefully, it will be buffering request bodies to temporary files on disk. So your data might not really be going to /dev/null - it might be going to a disk. Most likely not want you want at all. I'll get a CVE allocated for this bug right away.