CVE-2025-59583: Penci Filter Everything XSS Vulnerability

CVE-2025-59583 Overview

CVE-2025-59583 is a DOM-based Cross-Site Scripting (XSS) vulnerability in the PenciDesign Penci Filter Everything WordPress plugin. The flaw stems from improper neutralization of user-supplied input during web page generation [CWE-79]. The vulnerability affects all versions of penci-filter-everything up to and including version 1.7. An attacker can craft a malicious URL or input that, when processed by the client-side script, executes arbitrary JavaScript in a victim's browser session. Exploitation requires low privileges and user interaction, and can result in session compromise, content modification, or redirection to attacker-controlled resources within the WordPress site context.

Critical Impact
A successful attack executes attacker-controlled JavaScript in the victim's browser, allowing session theft, defacement, or unauthorized actions performed with the victim's WordPress privileges.

Affected Products

PenciDesign Penci Filter Everything WordPress plugin
All versions from n/a through < 1.7
WordPress sites with penci-filter-everything installed and active

Discovery Timeline

2025-09-22 - CVE-2025-59583 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-59583

Vulnerability Analysis

The vulnerability is a DOM-based XSS issue in the Penci Filter Everything plugin. DOM-based XSS occurs when client-side JavaScript reads attacker-controlled data from a source such as location.hash, location.search, or document.referrer and writes it into the Document Object Model (DOM) without proper sanitization or encoding. In this plugin, filter parameters processed on the client side are reflected into the page without adequate escaping, allowing script injection. The attack executes entirely in the browser, meaning server-side logging may not capture the malicious payload. Because the plugin implements filtering functionality for post grids and archives, the vulnerable sinks are reachable on public-facing pages.

Root Cause

The root cause is missing output encoding in the plugin's client-side filter handling logic. User-controllable input is inserted into DOM sinks such as innerHTML or equivalent jQuery methods without escaping HTML metacharacters. This allows an attacker to inject <script> tags or event handlers that execute in the victim's browser.

Attack Vector

An attacker crafts a URL containing a malicious payload in a filter parameter and delivers it to a target through phishing, social engineering, or a malicious referrer. When the victim clicks the link and the page loads, the plugin's JavaScript parses the parameter and injects it into the DOM, triggering script execution. The attack requires user interaction (UI:R) and can pivot across security scopes (S:C), impacting both the plugin context and the wider WordPress site session. Because privileges required are low, any authenticated user, including subscribers, can be induced to trigger the payload against themselves or other users.

No verified public proof-of-concept code is available. Refer to the Patchstack Vulnerability Report for advisory details.

Detection Methods for CVE-2025-59583

Indicators of Compromise

Unusual URL parameters containing HTML tags, javascript: URIs, or event handlers such as onerror= and onload= targeting filter endpoints on pages using penci-filter-everything.
Unexpected outbound requests from user browsers to attacker-controlled domains after visiting filter-enabled pages.
WordPress administrator or editor sessions performing unexpected actions immediately after visiting a crafted URL.

Detection Strategies

Inspect web server access logs for query strings containing encoded script fragments such as %3Cscript%3E, %3Cimg, or onerror%3D targeting pages that render the Penci Filter Everything widget.
Deploy Content Security Policy (CSP) reporting to capture inline script violations originating from filter interactions.
Review browser telemetry and endpoint DNS logs for connections to unknown domains following visits to pages hosting the plugin.

Monitoring Recommendations

Enable a web application firewall (WAF) rule set that flags reflected script payloads in URL parameters processed by WordPress front-end pages.
Audit the installed WordPress plugin inventory and version list to identify any host still running penci-filter-everything at version 1.7 or earlier.
Monitor WordPress user activity logs for privilege changes, new administrator accounts, or content modifications occurring shortly after user browsing sessions on public pages.

How to Mitigate CVE-2025-59583

Immediate Actions Required

Update the Penci Filter Everything plugin to a version newer than 1.7 once the vendor releases a patched release.
Deactivate and remove the plugin on any site that does not require its functionality until a fix is confirmed.
Review WordPress user accounts for signs of compromise and rotate credentials for privileged accounts that may have visited crafted URLs.

Patch Information

At the time of publication, the advisory indicates the vulnerability affects Penci Filter Everything versions through < 1.7. Site administrators should consult the Patchstack Vulnerability Report and the PenciDesign vendor channels for the latest patched version and apply it through the WordPress plugin update mechanism.

Workarounds

Apply a WAF rule that blocks HTTP requests containing HTML tags or JavaScript event handlers in filter query parameters directed at the affected plugin endpoints.
Deploy a strict Content Security Policy that disallows inline script execution (script-src 'self') to limit the impact of injected payloads.
Restrict access to filter-enabled pages behind authentication where the site's use case permits, reducing the pool of potential victims.

bash

# Example nginx rule to block obvious XSS payloads in query strings
if ($args ~* "(<|%3C)script|onerror=|javascript:") {
    return 403;
}