CVE-2026-1922: Events Calendar Shortcode XSS Vulnerability

CVE-2026-1922 Overview

The Events Calendar Shortcode & Block plugin for WordPress is vulnerable to Stored Cross-Site Scripting (XSS) via the plugin's ecs-list-events shortcode message attribute in all versions up to, and including, 3.1.2. The vulnerability arises due to insufficient input sanitization and output escaping on user-supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

Critical Impact

Authenticated attackers with contributor-level privileges can inject persistent malicious scripts that execute in the browsers of any user viewing affected pages, potentially leading to session hijacking, credential theft, or further site compromise.

Affected Products

• The Events Calendar Shortcode & Block plugin for WordPress versions up to and including 3.1.2

Discovery Timeline

• February 10, 2026 - CVE-2026-1922 published to NVD
• February 10, 2026 - Last updated in NVD database

Technical Details for CVE-2026-1922

Vulnerability Analysis

This Stored Cross-Site Scripting vulnerability exists within the ecs-list-events shortcode functionality of The Events Calendar Shortcode & Block plugin. The core issue stems from CWE-79 (Improper Neutralization of Input During Web Page Generation), where user-controlled input passed through the message attribute is not properly sanitized before being rendered in the page output.

When a user with contributor-level permissions or higher creates or edits content containing the vulnerable shortcode, they can inject malicious JavaScript code through the message attribute. This script is then stored in the WordPress database and executed in the browser context of any visitor who views the page containing the malicious shortcode.

The network-accessible nature of this vulnerability combined with the low complexity required for exploitation makes it particularly concerning for multi-author WordPress sites. Since the attack requires no user interaction beyond normal page viewing, the malicious payload persists and executes automatically.

Root Cause

The vulnerability originates from insufficient input validation and output escaping in the shortcode processing logic located at line 486 of the-events-calendar-shortcode.php. The plugin fails to properly sanitize the message attribute value before incorporating it into the HTML output, allowing HTML and JavaScript injection. WordPress provides functions like esc_html(), esc_attr(), and wp_kses() for sanitizing user input, but these protections were not adequately applied to the message attribute handler.

Attack Vector

The attack vector is network-based and requires the attacker to have authenticated access with at least contributor-level permissions on the target WordPress site. The attack flow involves:

1. An authenticated attacker with contributor privileges creates or edits a post/page
2. The attacker inserts the ecs-list-events shortcode with a malicious payload in the message attribute
3. When the content is saved, the malicious script is stored in the WordPress database
4. Any user (including administrators) who views the page triggers the stored XSS payload
5. The malicious script executes in the victim's browser context, potentially stealing session cookies, performing actions on behalf of the victim, or redirecting to phishing pages

The vulnerability mechanism involves improper handling of the shortcode's message attribute. The plugin fails to sanitize special characters and script content before rendering the attribute value in the page output. For detailed technical analysis, refer to the WordPress Plugin Source File and the Wordfence Vulnerability Report.

Detection Methods for CVE-2026-1922

Indicators of Compromise

• Posts or pages containing ecs-list-events shortcodes with suspicious JavaScript or HTML in the message attribute
• Unexpected <script> tags, event handlers (e.g., onerror, onload), or encoded payloads within shortcode attributes
• User complaints about unexpected browser behavior, redirects, or pop-ups when viewing event listing pages
• Database entries in wp_posts table containing malicious script patterns within shortcode attributes

Detection Strategies

• Implement database auditing to search for potentially malicious patterns within shortcode attributes in the wp_posts table
• Deploy Web Application Firewall (WAF) rules to detect and block XSS payloads in POST requests to WordPress admin endpoints
• Use WordPress security plugins that scan content for suspicious shortcode parameters and JavaScript injection attempts
• Monitor HTTP response content for unexpected script injections on pages utilizing the events calendar shortcode

Monitoring Recommendations

• Enable comprehensive logging of post/page edits, particularly for users with contributor-level access
• Implement Content Security Policy (CSP) headers to detect and report inline script execution attempts
• Configure alerting for bulk content modifications or shortcode insertions by non-administrator accounts
• Regularly audit contributor and author account activity for suspicious content creation patterns

How to Mitigate CVE-2026-1922

Immediate Actions Required

• Update The Events Calendar Shortcode & Block plugin to the latest patched version (post-3.1.2)
• Audit existing posts and pages for potentially malicious content in ecs-list-events shortcode message attributes
• Review and limit contributor-level account access until the plugin is updated
• Implement a Web Application Firewall with XSS protection rules as a temporary defensive layer

Patch Information

The plugin maintainers have released a security update addressing this vulnerability. The fix can be reviewed in the WordPress Changeset Update. Site administrators should update to the latest version available through the WordPress plugin repository immediately.

For additional technical details about the vulnerability and the fix, consult the Wordfence Vulnerability Report.

Workarounds

• Temporarily disable The Events Calendar Shortcode & Block plugin if immediate patching is not possible
• Restrict contributor and author role capabilities to prevent shortcode insertion until patched
• Implement server-side input filtering to strip potentially malicious content from shortcode attributes
• Deploy Content Security Policy headers to mitigate the impact of any successful XSS exploitation

# WordPress CLI command to update the plugin
wp plugin update the-events-calendar-shortcode

# Search database for potentially malicious shortcode usage
wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%ecs-list-events%message=%' AND post_content REGEXP '<script|javascript:|onerror|onload'"