WP CTA <= 2.1.2 - Authenticated (Administrator+) Server-Side Request Forgery

The WP CTA plugin for WordPress is vulnerable to Server-Side Request Forgery via the 'sticky_s_media' parameter in imported JSON files in all versions up to, and including, 2.1.2. This is due to the import_sidebars() function passing user-supplied URLs from imported JSON data to file_get_contents() with only FILTER_VALIDATE_URL validation (which allows internal IPs). This makes it possible for authenticated attackers, with Administrator-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. The response content is saved as a WordPress media attachment, making this a full-read SSRF.