CVE-2025-39428: Gravity Forms CSS Themes Stored XSS Flaw

CVE-2025-39428 Overview

CVE-2025-39428 is a stored Cross-Site Scripting (XSS) vulnerability in the Maros Pristas Gravity Forms CSS Themes with Fontawesome and Placeholders WordPress plugin. The flaw stems from improper neutralization of input during web page generation, classified under [CWE-79]. It affects all plugin versions up to and including 8.5. An authenticated attacker with high privileges can inject persistent JavaScript payloads that execute in the browsers of users who view the affected pages. Because the scope is changed (S:C), the injected script can impact resources beyond the vulnerable component.

Critical Impact
Stored XSS enables persistent JavaScript execution in the context of the WordPress site, potentially leading to session hijacking, credential theft, and administrative account takeover.

Affected Products

Gravity Forms CSS Themes with Fontawesome and Placeholders (plugin slug: gravity-forms-css-themes-with-fontawesome-and-placeholder-support)
All versions from n/a through <= 8.5
WordPress installations running the vulnerable plugin

Discovery Timeline

2025-04-17 - CVE-2025-39428 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-39428

Vulnerability Analysis

The vulnerability is a stored Cross-Site Scripting (XSS) flaw within the plugin's input handling code. The plugin fails to sanitize or encode user-supplied input before persisting it and later rendering it in the WordPress front-end or admin interface. As a result, an attacker with sufficient privileges can store malicious HTML or JavaScript that executes when other users load the page. Exploitation requires user interaction, and the CVSS scope change (S:C) reflects that injected script can affect components beyond the vulnerable plugin, such as authenticated sessions of administrators viewing the injected content. The EPSS probability is 0.264%.

Root Cause

The root cause is missing output encoding and input sanitization when the plugin processes form-related fields, CSS theme configuration, or placeholder values. Data supplied through the plugin's administrative interfaces is stored in the WordPress database and later reflected into HTML output without applying WordPress escaping functions such as esc_html(), esc_attr(), or wp_kses(). This allows attacker-controlled markup to be interpreted as executable script by the browser.

Attack Vector

The attack requires network access to the WordPress site and an authenticated account with high privileges, typically administrator or editor level. The attacker submits a crafted payload containing JavaScript into a plugin-controlled field. Once stored, the payload executes when a victim, such as another administrator, loads the affected view. Successful exploitation can be leveraged to steal session cookies, perform actions on behalf of the victim, pivot to install malicious plugins, or create rogue administrator accounts.

No public proof-of-concept code has been verified for this vulnerability. See the Patchstack advisory for additional technical detail.

Detection Methods for CVE-2025-39428

Indicators of Compromise

Unexpected <script>, <iframe>, or event-handler attributes (for example onerror, onload) stored inside plugin-managed WordPress database records.
New or unrecognized WordPress administrator accounts created shortly after an authenticated user viewed plugin-managed content.
Outbound HTTP requests from browsers of administrative users to unfamiliar domains after loading a Gravity Forms page.
WordPress wp_options or plugin option rows containing HTML entities that resolve to executable JavaScript.

Detection Strategies

Query the WordPress database for plugin option and post rows containing <script, javascript:, or on\w+= patterns.
Review web server access logs for POST requests to plugin admin endpoints followed by administrative page loads from other sessions.
Enable a Content Security Policy (CSP) in report-only mode to identify inline script executions originating from plugin-rendered pages.

Monitoring Recommendations

Monitor WordPress audit logs for changes to plugin settings performed by high-privilege accounts.
Alert on creation of new administrator users, modifications to wp_users, or unexpected plugin and theme installations.
Track browser telemetry from administrative workstations for anomalous outbound requests originating from WordPress admin sessions.

How to Mitigate CVE-2025-39428

Immediate Actions Required

Deactivate the Gravity Forms CSS Themes with Fontawesome and Placeholders plugin until a patched release is confirmed installed.
Audit all administrator and editor accounts, rotate credentials, and enforce multi-factor authentication.
Inspect plugin-managed database records for stored payloads and remove any injected HTML or script content.
Invalidate active WordPress sessions to revoke any cookies that may have been captured through XSS.

Patch Information

As of the latest NVD update, no fixed version beyond 8.5 has been recorded in the enriched CVE data. Administrators should consult the Patchstack advisory and the plugin author for updated release information. If no patch is available, uninstall the plugin and replace it with a maintained alternative.

Workarounds

Restrict access to WordPress admin endpoints using IP allowlists, VPN gateways, or a web application firewall.
Apply virtual patching via a WAF ruleset that blocks HTML tags and event-handler attributes in requests to plugin endpoints.
Enforce a strict Content Security Policy that disallows inline scripts and untrusted script sources on the WordPress site.
Limit high-privilege accounts and apply least-privilege role assignments to reduce the pool of users capable of exploiting the flaw.

bash

# Example: disable the vulnerable plugin using WP-CLI
wp plugin deactivate gravity-forms-css-themes-with-fontawesome-and-placeholder-support
wp plugin delete gravity-forms-css-themes-with-fontawesome-and-placeholder-support