AI Agent by SiteGround <= 1.2.7 - Missing Authorization to Authenticated (Contributor+) Arbitrary Media Upload via /generate-content REST Endpoint

The AI Agent by SiteGround plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 1.2.7. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for unauthenticated attackers to upload images to the WordPress media library, bypassing the upload_files capability restriction that Contributors are normally subject to, as authenticated attackers with Contributor-level access or above can satisfy the endpoint's nonce and permission checks. The sg_ai_studio_gutenberg_nonce required by the endpoint is emitted to any user with block editor access — including Contributors — making the absent upload_files check the sole barrier to exploitation.