Local Syndication <= 1.5a - Authenticated (Contributor+) Server-Side Request Forgery via Shortcode

Summary

The Local Syndication plugin for WordPress is vulnerable to Server-Side Request Forgery in all versions up to, and including, 1.5a via the `url` parameter in the `[syndicate_local]` shortcode. This is due to the use of `wp_remote_get()` instead of `wp_safe_remote_get()` which lacks protections against requests to internal/private IP addresses and localhost. This makes it possible for authenticated attackers, with Contributor-level access and above, to make web requests to arbitrary locations originating from the web application, which can be used to query and modify information from internal services, scan internal networks, and access resources that should not be accessible from external networks.