CVE-2025-11807: Mixlr Shortcode WordPress Plugin XSS Flaw

CVE-2025-11807 Overview

The Mixlr Shortcode plugin for WordPress contains a stored Cross-Site Scripting (XSS) vulnerability affecting all versions up to and including 1.0.1. The flaw resides in the mixlr shortcode handler, which fails to properly sanitize and escape the url attribute before rendering it in page output. Authenticated users with contributor-level access or higher can inject arbitrary JavaScript that executes in the browsers of visitors who view the affected pages. The weakness is tracked as [CWE-79] (Improper Neutralization of Input During Web Page Generation).

Critical Impact
Contributor-level accounts can persist arbitrary JavaScript in published content, enabling session theft, administrative action forgery, and redirection of site visitors.

Affected Products

WordPress Mixlr Shortcode plugin versions 1.0.0 and earlier
WordPress Mixlr Shortcode plugin version 1.0.1
Any WordPress site permitting contributor-level or higher accounts to use the mixlr shortcode

Discovery Timeline

2025-10-22 - CVE-2025-11807 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-11807

Vulnerability Analysis

The Mixlr Shortcode plugin registers a mixlr shortcode that accepts a url attribute. This attribute is embedded directly into the HTML the plugin generates, without adequate sanitization or output escaping. When an authenticated contributor inserts the shortcode into a post or page, the supplied url value is stored in the database. Each time a visitor loads the rendered content, the browser executes any script payload the attacker placed in that attribute.

Because the payload is stored, it fires for every viewer, including administrators. An attacker who lures an administrator to view an injected post can hijack the administrative session, create new privileged users, or modify site content. The vulnerability requires only the ability to author content, which is granted to standard WordPress contributor accounts. Plugin source is available at the WordPress Plugin Code Snippet.

Root Cause

The plugin passes the url shortcode attribute into HTML output without applying WordPress escaping functions such as esc_url() or esc_attr(). Input sanitization on attribute assignment is also absent, so raw markup and script content survive the storage-to-render round trip.

Attack Vector

Exploitation follows a standard stored XSS pattern. An attacker authenticates as a contributor, edits a draft, and inserts a mixlr shortcode where the url attribute contains a JavaScript payload embedded via quote-breaking or event-handler injection. Once the draft is submitted and later viewed by any authenticated user, the payload executes in that user's session context. See the Wordfence Vulnerability Analysis for the confirmed exploitation path.

// No verified proof-of-concept code is published for CVE-2025-11807.
// Refer to the Wordfence advisory linked above for technical detail.

Detection Methods for CVE-2025-11807

Indicators of Compromise

Post or page revisions containing [mixlr url="..."] shortcodes whose url value includes <, >, javascript:, onerror=, or onload= fragments
Unexpected outbound requests from visitor browsers to attacker-controlled domains after loading pages that embed the mixlr shortcode
New administrator accounts, altered user roles, or modified wp_options values created shortly after a contributor account edited content

Detection Strategies

Query the wp_posts table for post_content entries matching the mixlr shortcode and inspect the url attribute for HTML metacharacters
Review WordPress activity logs for contributor accounts publishing or updating posts containing the mixlr shortcode
Monitor web server access logs for requests to posts embedding the plugin's shortcode paired with anomalous referrer or user-agent patterns

Monitoring Recommendations

Enable a web application firewall (WAF) rule set that flags stored XSS payloads in WordPress shortcode attributes
Alert on privilege changes and new administrator account creation events in WordPress
Track plugin version inventory across WordPress sites to identify unpatched installations of Mixlr Shortcode

How to Mitigate CVE-2025-11807

Immediate Actions Required

Disable or uninstall the Mixlr Shortcode plugin until a patched release is confirmed available on the WordPress Mixlr Shortcode Plugin page
Audit all posts and pages for existing mixlr shortcodes and remove any containing suspicious url values
Restrict contributor and author role assignments to trusted users and require multi-factor authentication for content editors

Patch Information

At the time of NVD publication, all versions up to and including 1.0.1 are affected. Site administrators should monitor the plugin's WordPress.org listing for a fixed release and apply it as soon as it is published. Until then, treat the plugin as vulnerable in every deployed version.

Workarounds

Remove the plugin entirely and embed Mixlr content through alternative trusted methods
Deploy a WAF rule that blocks shortcode attributes containing HTML tags or javascript: URIs
Reduce the privileges of untrusted contributors or move them to a role that cannot publish shortcodes

bash

# List posts referencing the vulnerable shortcode for review
wp post list --post_type=any --format=ids --s='[mixlr'

# Deactivate the plugin until a fix is released
wp plugin deactivate mixlr-shortcode