CVE-2026-2396: List View Google Calendar Plugin XSS Flaw

CVE-2026-2396 Overview

The List View Google Calendar plugin for WordPress is vulnerable to Stored Cross-Site Scripting (XSS) via the event description in all versions up to, and including, 7.4.3 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level access, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.

Critical Impact

Authenticated attackers with administrator privileges can inject persistent malicious scripts that execute in the browsers of any user viewing affected calendar event pages, potentially leading to session hijacking, credential theft, or further compromise of the WordPress installation.

Affected Products

• List View Google Calendar plugin for WordPress versions up to and including 7.4.3
• WordPress multi-site installations with the vulnerable plugin
• WordPress installations where unfiltered_html capability has been disabled

Discovery Timeline

• 2026-04-15 - CVE CVE-2026-2396 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2026-2396

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The vulnerability exists because the plugin fails to properly sanitize user-supplied input in event descriptions before rendering them on the page. When an administrator creates or edits a Google Calendar event with a malicious payload in the description field, the unsanitized content is stored in the database and subsequently rendered without proper output escaping.

The attack requires administrator-level authentication, which limits the attack surface, but presents significant risk in multi-site WordPress environments where administrators may have reduced privileges or where the unfiltered_html capability has been explicitly disabled as a security hardening measure.

Root Cause

The root cause of this vulnerability lies in the li.php file within the plugin's library directory. The affected code at line 6 of the li.php file does not implement proper input sanitization or output escaping when processing event description data. WordPress provides built-in functions such as esc_html(), esc_attr(), and wp_kses() for sanitizing output, but these protections are not utilized for the event description field, allowing script injection to persist in stored content.

Attack Vector

The attack vector is network-based and requires an authenticated attacker with administrator-level access to the WordPress installation. The attacker injects malicious JavaScript code into the event description field of a Google Calendar event. When any user—including other administrators or regular visitors—views a page containing the affected calendar listing, the injected script executes within their browser context.

In a typical exploitation scenario, an attacker with compromised or legitimately obtained admin credentials on a multi-site WordPress installation crafts a calendar event containing a malicious <script> tag or event handler attribute within the description. Since multi-site environments often restrict the unfiltered_html capability even for administrators, this vulnerability bypasses that security control by exploiting the plugin's failure to sanitize output.

Detection Methods for CVE-2026-2396

Indicators of Compromise

• Unusual or obfuscated JavaScript code appearing in Google Calendar event descriptions in the WordPress database
• Calendar event descriptions containing HTML event handlers such as onload, onerror, onclick, or onmouseover
• Database entries in calendar-related tables containing <script> tags or encoded script payloads
• Unexpected outbound network requests from client browsers when viewing calendar pages

Detection Strategies

• Review the wp_posts and any custom tables used by the List View Google Calendar plugin for suspicious content in event description fields
• Implement Web Application Firewall (WAF) rules to detect and block XSS payloads in form submissions to the WordPress admin area
• Deploy SentinelOne Singularity for endpoint detection to identify browser-based attacks resulting from XSS exploitation
• Monitor WordPress audit logs for unusual calendar event modifications by administrator accounts

Monitoring Recommendations

• Enable verbose logging for the WordPress admin area and review logs for suspicious activity related to calendar event editing
• Configure Content Security Policy (CSP) headers to restrict inline script execution and report violations
• Set up alerts for any modifications to calendar event content by monitoring database changes or using WordPress hooks
• Utilize SentinelOne's real-time monitoring capabilities to detect and respond to potential post-exploitation activity

How to Mitigate CVE-2026-2396

Immediate Actions Required

• Update the List View Google Calendar plugin to a patched version if one becomes available from the vendor
• Audit existing calendar event descriptions for any malicious content and sanitize or remove suspicious entries
• Consider temporarily disabling the List View Google Calendar plugin until a patch is released
• Implement Content Security Policy headers to mitigate the impact of any successful XSS exploitation

Patch Information

At the time of publication, organizations should monitor the Wordfence Vulnerability Report for updates on available patches. The vulnerable code is located in the library/tags/li.php file at line 6, where proper output escaping using WordPress functions like esc_html() or wp_kses_post() should be implemented.

Workarounds

• Limit administrator access to trusted users only and implement strong authentication controls including multi-factor authentication
• Manually add output escaping to the plugin code by modifying li.php to sanitize event description output using esc_html() or wp_kses_post()
• Deploy a Web Application Firewall with XSS protection rules to filter malicious input before it reaches the plugin
• For multi-site installations, consider network-deactivating the plugin until an official patch is available

# Configuration example for Content Security Policy header in WordPress
# Add to wp-config.php or .htaccess to help mitigate XSS impact

# Apache .htaccess configuration
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline';"

# Alternatively, add to functions.php
# add_action('send_headers', function() {
#     header("Content-Security-Policy: default-src 'self'; script-src 'self';");
# });