CVE-2026-55409: Filament Laravel XSS Vulnerability

CVE-2026-55409 Overview

CVE-2026-55409 is a stored Cross-Site Scripting (XSS) vulnerability in Filament, a collection of full-stack components for accelerated Laravel development. The flaw affects versions 3.0.0 through 3.3.52. A disabled RichEditor field renders its raw state without sanitizing HTML. When the field state is filled with data that was not previously sanitized, an attacker can inject malicious HTML or JavaScript. The payload executes in the browser of any user who views the form. The maintainers fixed the issue in version 3.3.53. The weakness is classified under CWE-79.

Critical Impact
Authenticated attackers can plant persistent JavaScript that executes in other users' browsers, enabling session theft, UI manipulation, and actions performed in the victim's context.

Affected Products

Filament 3.0.0 through 3.3.52
Laravel applications using the Filament admin panel with RichEditor fields
Forms that render RichEditor in a disabled state with unsanitized stored content

Discovery Timeline

2026-06-22 - CVE-2026-55409 published to NVD
2026-06-23 - Last updated in NVD database

Technical Details for CVE-2026-55409

Vulnerability Analysis

The Filament RichEditor component allows administrators to enter formatted HTML content stored in the application database. When the field is rendered in a disabled or read-only state, Filament outputs the stored value as raw HTML rather than passing it through an HTML sanitizer. The component assumes the field's state has already been sanitized upstream. Applications that fill the form state from untrusted sources, such as user submissions, third-party imports, or other components, propagate unfiltered markup into the rendered DOM. Any script tags, event handlers, or HTML attributes carrying JavaScript execute when an authenticated user loads the form.

Root Cause

The root cause is missing output encoding in the disabled-state rendering path of the RichEditor field [CWE-79]. The component trusts its input state to be sanitized HTML, but the design provides no enforcement at the rendering boundary. This violates the principle of treating all stored content as untrusted at output time.

Attack Vector

Exploitation requires an attacker to write a crafted payload into a field whose value later populates a disabled RichEditor. The attacker submits HTML containing JavaScript such as <img src=x onerror=...> or <script> blocks. When an administrator or other privileged user opens a form that renders this stored value in a disabled RichEditor, the browser parses and executes the payload. User interaction is required because the victim must view the affected form. The scope is changed because the script executes in the victim's authenticated browser context, allowing actions across the application session.

No verified public proof-of-concept code is available. Refer to the Filament GitHub Security Advisory GHSA-m9cv-24rx-8mv7 for vendor technical details.

Detection Methods for CVE-2026-55409

Indicators of Compromise

Stored database records in tables backing RichEditor fields containing <script>, onerror=, onload=, or javascript: patterns.
Unexpected outbound requests from authenticated admin sessions to attacker-controlled domains shortly after loading a form.
Filament admin panel sessions exhibiting DOM modifications, cookie exfiltration, or rapid privilege-change actions performed without user input.

Detection Strategies

Query database columns that feed RichEditor components for HTML event handlers and script tags using regex audits.
Enable a strict Content Security Policy (CSP) and monitor report-uri or report-to endpoints for inline script violations originating from Filament panel routes.
Review web server access logs for POST requests to Filament form endpoints that contain encoded <script> or onerror payloads.

Monitoring Recommendations

Log and alert on CSP violation reports tied to admin panel routes.
Monitor Laravel application logs for anomalous admin actions performed in rapid succession after a form view event.
Track Filament package versions across deployments and alert when any instance reports a version below 3.3.53.

How to Mitigate CVE-2026-55409

Immediate Actions Required

Upgrade Filament to version 3.3.53 or later in all Laravel applications.
Audit existing data stored in RichEditor-backed columns for malicious HTML and sanitize or purge offending records.
Rotate admin session tokens and credentials if evidence of exploitation is found in logs or database content.

Patch Information

The vulnerability is fixed in Filament 3.3.53. The patch ensures the disabled RichEditor state is sanitized before being rendered as HTML. See the GitHub Security Advisory GHSA-m9cv-24rx-8mv7 for fix details and release notes.

Workarounds

Apply HTML sanitization, such as HTMLPurifier or mews/purifier, to all input that populates RichEditor state before saving to the database.
Restrict access to forms containing disabled RichEditor fields to trusted administrators until the upgrade is applied.
Deploy a strict Content Security Policy that disallows inline scripts on Filament admin routes to limit payload execution.

bash

# Upgrade Filament via Composer
composer require filament/filament:^3.3.53 -W
composer update filament/filament
php artisan filament:upgrade
php artisan view:clear