CVE-2026-4406: Gravity Forms <= 2.9.30 - Reflected Cross-Site Scripting via 'form_ids' Parameter

The Gravity Forms plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the formids parameter in the gformgetconfig AJAX action in all versions up to, and including, 2.9.30. This is due to the GFCommon::sendjson() method outputting JSON-encoded data wrapped in HTML comment delimiters using echo and wpdie(), which serves the response with a Content-Type: text/html header instead of application/json. The wpjsonencode() function does not HTML-encode angle brackets within JSON string values, allowing injected HTML/script tags in formids array values to be parsed and executed by the browser. The required confignonce is generated with wpcreatenonce('gformconfigajax') and is publicly embedded on every page that renders a Gravity Forms form, making it identical for all unauthenticated visitors within the same 12-hour nonce tick. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. This vulnerability cannot be exploited against users who are authenticated on the target system, but could be used to alter the target page.