Patryk Siewert

The Nexa Blocks – Gutenberg Blocks, Page Builder for Gutenberg Editor & FSE plugin for WordPress is vulnerable to Server-Side Request Forgery (SSRF) in versions up to and including 1.1.1. This is due to the import demo() function accepting a user-supplied URL in the demo json file POST parameter and passing it directly to wp remote get() without any URL validation or restriction against internal or private network destinations. The nexa blocks nonce required for the AJAX action is publicly exposed in the HTML source of any frontend page where the plugin is active via wp localize script on the enqueue block assets hook, effectively making the nonce available to all visitors and bypassing any intended authentication barrier. This makes it possible for unauthenticated attackers to make server-side HTTP requests to arbitrary internal or external destinations, potentially exposing internal services, cloud metadata endpoints such as the AWS instance metadata service, localhost services, and other resources not intended to be publicly accessible. A secondary SSRF vector also exists whereby image URLs extracted from the attacker-controlled JSON response are subsequently fetched via a second wp remote get() call, allowing chained exploitation through a crafted JSON payload.