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

Vulnerability summary

CVE-2026-4406 is a medium (CVSS 4.7) Cross-site Scripting vulnerability in gravity forms. EPSS estimates a 0.39% chance of exploitation in the next 30 days, higher than 31.5% of scored vulnerabilities. Fixed in 2.9.31.

Timeline

1. 07-04-2026
   PublishedVulnerability first disclosed.
2. 08-04-2026
   Last modifiedVulnerability information updated.

Description

The Gravity Forms plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the `form_ids` parameter in the `gform_get_config` AJAX action in all versions up to, and including, 2.9.30. This is due to the `GFCommon::send_json()` method outputting JSON-encoded data wrapped in HTML comment delimiters using `echo` and `wp_die()`, which serves the response with a `Content-Type: text/html` header instead of `application/json`. The `wp_json_encode()` function does not HTML-encode angle brackets within JSON string values, allowing injected HTML/script tags in `form_ids` array values to be parsed and executed by the browser. The required `config_nonce` is generated with `wp_create_nonce('gform_config_ajax')` 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.

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.