Fediverse Embeds < 1.5.8 - Unauthenticated SSRF via Media Proxy

The Fediverse Embeds WordPress plugin before 1.5.8 does not validate the destination of the server-side request performed by an unauthenticated media-proxying endpoint, allowing anonymous users to make the site fetch arbitrary URLs, including internal and private-network addresses, and read back the response body. This results in a full-read Server-Side Request Forgery and open proxy.