The Pixelavo WordPress plugin before 1.5.4 registers an unauthenticated AJAX action, gated only by a nonce that it emits publicly on every front-end page, that forwards client-supplied event data to…

Summary

The Pixelavo WordPress plugin before 1.5.4 registers an unauthenticated AJAX action, gated only by a nonce that it emits publicly on every front-end page, that forwards client-supplied event data to the configured Facebook Conversions API using the administrator's stored access token. This allows an unauthenticated visitor to inject arbitrary conversion events into the administrator's Facebook ads account and exhaust the configured API quota.