The EmbedPress WordPress plugin before 4.6.1 does not validate user-supplied URLs before making server-side requests through unauthenticated endpoints, allowing unauthenticated attackers to induce the site to send HTTP requests to internal hosts and services that WordPress core URL validation does not cover (a blind Server-Side Request Forgery).
Weakness
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.