WordPress 5.3 Denial Of Service

WordPress is vulnerable to denial of service by abusing XMLRPC API. The system.multicall function lets you batch other API calls. Another API function is pingback.ping, which makes WordPress make a connection out to another site. If you batch a few thousand pingback.ping requests using the multicall feature, you can exhaust a variety of different resources on the server. This PoC will eat through Apache2's worker threads and will also make MySQL eat up more CPU and mem, possibly knocking over low-RAM VPS instances.