CVE-2025-50049: Modern Footnotes Stored XSS Vulnerability

CVE-2025-50049 Overview

CVE-2025-50049 is a stored Cross-Site Scripting (XSS) vulnerability in the Modern Footnotes plugin for WordPress, developed by prismtechstudios. The flaw affects all plugin versions up to and including 1.4.19. An authenticated user with contributor-level privileges or higher can inject malicious JavaScript into footnote content. The payload persists in the database and executes in the browsers of visitors and administrators who view the affected page. The issue is tracked as CWE-79: Improper Neutralization of Input During Web Page Generation.

Critical Impact
Authenticated attackers can store JavaScript payloads that execute in victim browsers, enabling session theft, administrative account takeover, and defacement of WordPress sites running Modern Footnotes <= 1.4.19.

Affected Products

Modern Footnotes WordPress plugin versions up to and including 1.4.19
WordPress sites with the modern-footnotes plugin installed and activated
Any content authors, editors, and site visitors interacting with pages containing malicious footnotes

Discovery Timeline

2025-06-20 - CVE-2025-50049 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-50049

Vulnerability Analysis

The Modern Footnotes plugin renders user-supplied footnote text inline within WordPress posts and pages. The plugin fails to properly neutralize HTML and JavaScript characters when processing footnote input before rendering it in the page output. Attackers can embed <script> tags or event-handler attributes within footnote shortcodes. When any user loads a page containing the malicious footnote, the browser executes the injected code in the origin of the WordPress site.

Exploitation requires low-privileged authentication and user interaction from a victim who visits an affected page. Because the payload persists in the database, a single injection affects every subsequent visitor, including administrators. Successful exploitation can result in session cookie theft, forced administrative actions via CSRF-chaining, credential harvesting through injected forms, and redirection to attacker-controlled infrastructure.

Root Cause

The root cause is missing or insufficient output encoding of footnote content. The plugin trusts input from users authorized to publish content and does not apply WordPress sanitization primitives such as wp_kses_post() or esc_html() before echoing footnote text into the DOM. This allows arbitrary HTML and script constructs to survive the render pipeline.

Attack Vector

An attacker authenticates to the target WordPress instance using a contributor, author, or editor account. The attacker inserts a Modern Footnotes shortcode containing a JavaScript payload into a post or page. The malicious content is saved to the database. When a visitor or administrator views the published content, the script executes in the victim's browser session. No additional privileges are required to weaponize the flaw once content authoring access is obtained.

Refer to the Patchstack XSS Vulnerability Advisory for the reported proof-of-concept details.

Detection Methods for CVE-2025-50049

Indicators of Compromise

Footnote content in wp_posts containing <script>, onerror=, onload=, or javascript: strings
Outbound requests from visitor browsers to unfamiliar domains after loading pages with Modern Footnotes shortcodes
New or modified administrator accounts created shortly after content authoring activity by a lower-privileged user
WordPress audit log entries showing post edits by contributor or author accounts followed by anomalous admin sessions

Detection Strategies

Query the WordPress database for modern_footnotes shortcode instances containing HTML tag delimiters or JavaScript event handlers
Deploy web application firewall rules to inspect POST bodies to wp-admin/post.php for script payloads within footnote parameters
Monitor server-rendered HTML for footnote-adjacent DOM nodes containing inline scripts or external script sources

Monitoring Recommendations

Enable WordPress plugin and content auditing to record all post revisions with author attribution
Forward WordPress and web server logs to a centralized analytics platform for correlation of authoring events with client-side anomalies
Alert on outbound connections from browsers rendering WordPress content to newly registered or low-reputation domains

How to Mitigate CVE-2025-50049

Immediate Actions Required

Update the Modern Footnotes plugin to a version later than 1.4.19 once the vendor releases a patched build
Audit all existing posts and pages for stored footnote payloads containing script tags or JavaScript event handlers
Review WordPress user accounts and revoke unnecessary contributor, author, or editor privileges
Rotate administrator session cookies and credentials if suspicious footnote content is discovered

Patch Information

At the time of publication, the vulnerability affects Modern Footnotes versions up to and including 1.4.19. Monitor the Patchstack advisory and the plugin's WordPress.org listing for a fixed release, then upgrade all affected installations.

Workarounds

Deactivate and remove the Modern Footnotes plugin until a fixed version is available
Restrict content authoring to trusted accounts and enforce multi-factor authentication for all editorial roles
Deploy a web application firewall rule that blocks HTML tags and JavaScript event handlers inside modern_footnotes shortcode parameters
Configure a strict Content Security Policy that disallows inline scripts and untrusted external script sources

bash

# Example WordPress WP-CLI commands to inventory and disable the plugin
wp plugin list --name=modern-footnotes --fields=name,status,version
wp plugin deactivate modern-footnotes
wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content REGEXP 'modern_footnotes.*(<script|onerror=|onload=|javascript:)';"