CVE-2025-57926: Passster Content Protector XSS Vulnerability

CVE-2025-57926 Overview

CVE-2025-57926 is a stored cross-site scripting (XSS) vulnerability in the WP Chill Passster plugin for WordPress, also distributed under the content-protector slug. The flaw exists in all versions up to and including 4.2.18 and stems from improper neutralization of user-supplied input during web page generation [CWE-79]. An authenticated attacker with low privileges can inject malicious script content that executes in the browser of any user who later views the affected page. Because the payload is stored server-side, exploitation persists across sessions until the malicious content is removed.

Critical Impact
Authenticated attackers can inject persistent JavaScript that executes in visitors' browsers, enabling session theft, credential harvesting, and administrative account takeover through targeted payloads.

Affected Products

WP Chill Passster (content-protector) WordPress plugin
All versions from initial release through 4.2.18
WordPress sites using Passster for content gating and password protection

Discovery Timeline

2025-09-22 - CVE-2025-57926 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-57926

Vulnerability Analysis

The vulnerability resides in how the Passster plugin processes and renders user-controlled input within its content-protection workflow. Input passed through plugin fields is not properly sanitized before being written to the database and echoed back into rendered pages. When a browser later loads a page containing the injected content, the payload executes in the site's origin.

Stored XSS in a WordPress plugin context is particularly effective because payloads persist across sessions and can target administrators who visit affected pages in the dashboard or on the front end. The scope-change component of the vulnerability indicates that a successful attack can affect resources beyond the vulnerable component itself, including authenticated administrator sessions.

Root Cause

The root cause is missing or insufficient output encoding on values supplied through Passster's protected-content configuration. WordPress provides sanitization helpers such as esc_html(), esc_attr(), and wp_kses() for exactly this class of input, but the affected code paths render attacker-controlled strings into HTML contexts without applying them.

Attack Vector

Exploitation requires an authenticated user with permission to configure or submit content that Passster processes. User interaction is also required, meaning a victim must load a page that renders the stored payload. Once triggered, the injected JavaScript runs with the privileges of the viewing user, which allows session token theft, forced administrative actions via the WordPress REST API, or the addition of persistent backdoor accounts. Full technical detail is available in the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-57926

Indicators of Compromise

Unexpected <script>, <iframe>, or on* event-handler attributes stored in Passster-managed post meta or plugin option rows.
New or modified WordPress administrator accounts created shortly after an authenticated low-privilege user edited Passster-protected content.
Outbound browser requests from administrator sessions to unfamiliar domains immediately after loading Passster-protected pages.

Detection Strategies

Query the WordPress database for Passster option and meta values containing HTML tags or JavaScript URI schemes such as javascript:.
Review web server access logs for POST requests to Passster admin-ajax or REST endpoints followed by GET requests that return responses containing script content.
Enable a Content Security Policy in report-only mode to surface unexpected inline script execution on pages served by the plugin.

Monitoring Recommendations

Alert on newly created WordPress users with the administrator role and on role escalations for existing accounts.
Monitor plugin file integrity and Passster version strings to confirm patched builds remain deployed.
Forward WordPress audit logs to a centralized SIEM to correlate content edits with subsequent privileged actions.

How to Mitigate CVE-2025-57926

Immediate Actions Required

Upgrade the WP Chill Passster plugin to a release later than 4.2.18 as soon as the vendor publishes a fixed version.
Audit all existing Passster-protected content and stored plugin options for injected HTML or JavaScript and remove any suspicious entries.
Rotate credentials and invalidate active sessions for administrator accounts that may have viewed affected pages.

Patch Information

At the time of publication, refer to the Patchstack Vulnerability Report for the latest patched version and vendor advisory. Apply plugin updates through the WordPress dashboard or via WP-CLI on a staging environment first.

Workarounds

Restrict Passster configuration permissions to trusted administrators until a patched release is installed.
Deploy a web application firewall rule that blocks HTML tags and JavaScript event handlers in requests to Passster admin endpoints.
Enforce a strict Content Security Policy that disallows inline scripts on pages rendered by the plugin.

bash

# Update the Passster plugin using WP-CLI once a fixed version is available
wp plugin update content-protector --version=<patched-version>

# Verify the installed version
wp plugin get content-protector --field=version