CVE-2024-13377 Overview
CVE-2024-13377 is a Stored Cross-Site Scripting (XSS) vulnerability in the Gravity Forms plugin for WordPress. The flaw affects all versions up to and including 2.9.1.3 and stems from insufficient input sanitization and output escaping on the alt parameter. Unauthenticated attackers can inject arbitrary JavaScript that executes in the browser of any user visiting an affected page. The vulnerability is classified under [CWE-79] (Improper Neutralization of Input During Web Page Generation).
Critical Impact
Unauthenticated attackers can persistently inject malicious scripts that execute in the browsers of site visitors and administrators, enabling session theft, account takeover, and content manipulation.
Affected Products
- Gravity Forms plugin for WordPress, all versions up to and including 2.9.1.3
- WordPress sites running vulnerable Gravity Forms installations
- Any web pages rendering form output that includes the alt parameter
Discovery Timeline
- 2025-01-17 - CVE-2024-13377 published to the National Vulnerability Database (NVD)
- 2026-04-15 - Last updated in the NVD database
Technical Details for CVE-2024-13377
Vulnerability Analysis
The vulnerability is a Stored Cross-Site Scripting flaw within the Gravity Forms plugin. The plugin fails to properly sanitize user-supplied input passed through the alt parameter before storing it. When the stored value is later rendered, the plugin also fails to apply correct output escaping. The result is that attacker-controlled markup, including <script> tags or event-handler attributes, is written directly into the HTML response.
Because the payload is persisted, it executes for every subsequent visitor to the affected page. Exploitation requires no authentication and no user interaction beyond visiting the page. Successful attacks can hijack authenticated administrator sessions, exfiltrate cookies, perform actions on behalf of users, or redirect victims to attacker-controlled infrastructure.
Root Cause
The root cause is twofold: missing input sanitization at the point where the alt parameter is accepted, and missing context-appropriate output escaping when the stored value is reflected into HTML. Neither defensive control is applied, so any HTML or JavaScript supplied by an attacker is preserved verbatim through the persistence and rendering pipeline.
Attack Vector
The attack vector is network-based and requires no privileges. An attacker submits a crafted payload to the alt parameter on a vulnerable Gravity Forms endpoint. The malicious value is stored by the plugin. When any user, including site administrators, loads a page that renders the stored value, the injected script executes in that user's browser session under the origin of the affected WordPress site.
No verified public exploit code is available at this time. Technical details are described in the Wordfence Vulnerability Report.
Detection Methods for CVE-2024-13377
Indicators of Compromise
- Form entries or page content containing <script> tags, javascript: URIs, or HTML event handlers such as onerror=, onload=, or onclick= in fields associated with the alt parameter
- Unexpected outbound requests from administrator browsers to unfamiliar domains shortly after loading WordPress admin pages
- New or modified WordPress administrator accounts created without an audit trail
- Anomalous changes to plugin or theme files following administrator activity
Detection Strategies
- Scan the WordPress database, particularly tables used by Gravity Forms entries, for HTML or JavaScript content in stored alt values
- Inspect web server access logs for POST requests to Gravity Forms endpoints carrying HTML-encoded or raw script payloads in the alt parameter
- Deploy a Web Application Firewall (WAF) ruleset that flags XSS payload patterns targeting WordPress form submission endpoints
Monitoring Recommendations
- Monitor administrator session activity for unusual API calls or content changes immediately after viewing pages containing form output
- Alert on creation of new privileged WordPress users or modifications to user roles
- Track Gravity Forms plugin version across all managed WordPress instances and flag any still running 2.9.1.3 or earlier
How to Mitigate CVE-2024-13377
Immediate Actions Required
- Update the Gravity Forms plugin to a version later than 2.9.1.3 as published in the Gravity Forms Change Log
- Audit existing form entries and rendered pages for stored XSS payloads and remove any malicious content
- Rotate WordPress administrator passwords and invalidate active sessions after patching
- Review WordPress audit logs for unauthorized administrative actions taken since the vulnerability became exploitable
Patch Information
The vendor has released a fixed version of Gravity Forms that addresses the input sanitization and output escaping deficiencies in the handling of the alt parameter. Refer to the official Gravity Forms Change Log for the specific patched release and upgrade instructions.
Workarounds
- Deploy a Web Application Firewall rule that blocks HTML and JavaScript payloads in form submission parameters until patching is complete
- Restrict access to Gravity Forms submission endpoints with IP allow-listing where business requirements permit
- Apply a strict Content Security Policy (CSP) that disallows inline scripts to reduce the impact of any stored payloads
# Example Content-Security-Policy header to mitigate inline script execution
# Add to your web server or WordPress security plugin configuration
Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
