CVE-2025-5842: Modern Design Library XSS Vulnerability

CVE-2025-5842 Overview

The Modern Design Library plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability in the class parameter. The flaw affects all versions up to and including 1.1.4. Insufficient input sanitization and output escaping allow authenticated attackers with Contributor-level access or above to inject arbitrary web scripts into pages. The injected scripts execute whenever a user visits an affected page. The vulnerability is tracked under CWE-79 and impacts the mdl-shortcodes plugin distributed by getbutterfly.

Critical Impact
Contributor-level users can persist malicious JavaScript into rendered pages, enabling session theft, forced redirects, and administrator account takeover when privileged users view the injected content.

Affected Products

Getbutterfly Modern Design Library (mdl-shortcodes) plugin for WordPress
All versions up to and including 1.1.4
WordPress sites accepting Contributor-level (or higher) registrations

Discovery Timeline

2025-06-26 - CVE-2025-5842 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-5842

Vulnerability Analysis

The Modern Design Library plugin exposes shortcodes that accept a class attribute controlling the CSS class applied to rendered elements. The plugin echoes the attribute value into HTML output without sufficient sanitization or contextual escaping. An attacker supplying a crafted class value can break out of the attribute context and inject arbitrary HTML or JavaScript.

Because the payload is stored in post or page content, execution occurs each time the affected page renders in a browser. This turns any Contributor account into a foothold for targeting administrators, editors, and site visitors. Session cookies, CSRF tokens, and administrative actions become accessible to the injected script under the origin of the WordPress site.

The vulnerable code path is documented at the plugin source line 197. Additional analysis is available in the Wordfence vulnerability report.

Root Cause

The plugin fails to apply esc_attr() or a comparable escaping routine to the class shortcode parameter before emitting it into HTML markup. The absence of an allowlist for CSS class characters, combined with missing output escaping, permits attribute-context breakout and script injection.

Attack Vector

Exploitation requires an authenticated WordPress account with Contributor role or higher. The attacker inserts a shortcode using the vulnerable plugin and supplies a malicious class attribute containing quote characters followed by an HTML event handler or <script> tag. When the resulting page is previewed, published, or viewed by another user, the payload executes in that user's browser context.

See the official plugin advisory changeset for the vendor's fix reference and technical details of the corrected code path.

Detection Methods for CVE-2025-5842

Indicators of Compromise

Post or page content containing Modern Design Library shortcodes with unusual class attribute values containing quotes, angle brackets, on*= event handlers, or javascript: URIs.
New or modified posts authored by Contributor accounts that reference mdl- shortcodes.
Unexpected outbound requests from browser sessions of administrators shortly after viewing pages that render plugin shortcodes.

Detection Strategies

Scan the wp_posts table for shortcode invocations from the plugin combined with suspicious class attribute payloads.
Compare the installed plugin version against 1.1.4 and flag any WordPress site running the vulnerable release.
Deploy web application firewall rules that inspect shortcode attribute values for HTML control characters and script tags.

Monitoring Recommendations

Alert on newly promoted or newly created Contributor, Author, and Editor accounts.
Monitor edits to published pages that add or modify Modern Design Library shortcodes.
Track browser-side errors, mixed-content warnings, and unexpected script loads originating from WordPress-served pages.

How to Mitigate CVE-2025-5842

Immediate Actions Required

Update the Modern Design Library plugin to a version later than 1.1.4 that includes the fix from changeset 3317171.
Audit all Contributor, Author, and Editor accounts and revoke access for any that are unrecognized or inactive.
Review recently modified posts and pages for injected shortcode payloads and remove or sanitize affected content.

Patch Information

The vendor addressed the flaw in the plugin trunk. Refer to the WordPress plugin changeset for the corrective commit and the plugin developer page for release information. Site owners should update through the WordPress plugin dashboard and verify the installed version reflects a release later than 1.1.4.

Workarounds

Deactivate the Modern Design Library plugin until the site can be updated to a patched version.
Restrict user registration and lower the default new-user role below Contributor to prevent unauthenticated exploitation paths.
Deploy a web application firewall rule that blocks shortcode attribute values containing <, >, ", ', or on\w+= sequences.

bash

# Verify the currently installed plugin version via WP-CLI
wp plugin get mdl-shortcodes --field=version

# Update the plugin to the latest patched release
wp plugin update mdl-shortcodes

# If a patched version is not yet available, deactivate the plugin
wp plugin deactivate mdl-shortcodes