CVE-2026-1891: Simple Football Scoreboard XSS Vulnerability

CVE-2026-1891 Overview

The Simple Football Scoreboard plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability in the ytmr_fb_scoreboard shortcode. All versions up to and including 1.0 are affected due to insufficient input sanitization and output escaping on user-supplied attributes. This vulnerability allows authenticated attackers with Contributor-level access or higher to inject arbitrary web scripts into WordPress pages, which execute whenever any user accesses the compromised page.

Critical Impact

Authenticated attackers can inject persistent malicious scripts that execute in the context of other users' browsers, potentially leading to session hijacking, credential theft, or malicious content distribution to site visitors.

Affected Products

• Simple Football Scoreboard WordPress Plugin version 1.0 and earlier

Discovery Timeline

• 2026-03-21 - CVE CVE-2026-1891 published to NVD
• 2026-03-23 - Last updated in NVD database

Technical Details for CVE-2026-1891

Vulnerability Analysis

This Stored Cross-Site Scripting vulnerability resides in the shortcode handler for ytmr_fb_scoreboard within the Simple Football Scoreboard plugin. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). The flaw enables attackers with at least Contributor-level permissions to craft malicious shortcode attributes that are stored in the WordPress database and rendered without proper sanitization when pages are viewed.

The attack can be executed remotely over the network and requires no user interaction beyond accessing the injected page. Because the malicious payload is stored server-side, every user who views the compromised page will have the script execute in their browser context, potentially affecting site administrators with elevated privileges.

Root Cause

The root cause is insufficient input sanitization and output escaping on user-supplied attributes within the ytmr_fb_scoreboard shortcode implementation. When the shortcode processes user-provided parameters, it fails to properly sanitize input before storing it and does not escape output when rendering the shortcode content on the page. This allows JavaScript or HTML content injected through shortcode attributes to be rendered directly in the browser DOM.

Attack Vector

The attack vector is network-based and requires authentication with at least Contributor-level access to the WordPress site. An attacker can exploit this vulnerability by creating or editing a post or page containing the vulnerable shortcode with malicious attribute values. The injected script persists in the WordPress database and executes whenever any user—including administrators—views the page containing the malicious shortcode.

The vulnerability exists in the shortcode handler located at line 310 of ytmr_simple_football_scoreboard.php. Attackers can craft shortcode attributes containing JavaScript event handlers or script tags that bypass insufficient sanitization filters.

Detection Methods for CVE-2026-1891

Indicators of Compromise

• Unusual or obfuscated JavaScript code within WordPress posts or pages using the ytmr_fb_scoreboard shortcode
• Shortcode attributes containing HTML event handlers such as onerror, onload, onclick, or onmouseover
• Database entries in wp_posts table containing suspicious script content within shortcode parameters
• Browser console errors or unexpected network requests originating from pages using the scoreboard plugin

Detection Strategies

• Review WordPress posts and pages for instances of the ytmr_fb_scoreboard shortcode with suspicious attribute values
• Implement Content Security Policy (CSP) headers to detect and block inline script execution
• Monitor WordPress audit logs for content modifications by Contributor-level users containing script elements
• Use web application firewalls (WAF) with XSS detection rules to identify malicious payload attempts

Monitoring Recommendations

• Enable WordPress activity logging to track all post and page modifications by authenticated users
• Configure security plugins such as Wordfence to alert on potential XSS patterns in content
• Monitor browser-side errors and unexpected JavaScript execution using endpoint detection tools
• Review server access logs for suspicious POST requests to WordPress editor endpoints

How to Mitigate CVE-2026-1891

Immediate Actions Required

• Audit all existing posts and pages using the ytmr_fb_scoreboard shortcode for malicious content
• Consider temporarily disabling or removing the Simple Football Scoreboard plugin until a patch is available
• Review and restrict Contributor-level user accounts to trusted individuals only
• Implement a Web Application Firewall (WAF) with XSS filtering capabilities

Patch Information

As of the last NVD update on 2026-03-23, no official patch has been confirmed for this vulnerability. Organizations should monitor the WordPress Plugin Source Code for updates and check the Wordfence Vulnerability Report for remediation guidance.

Workarounds

• Remove the Simple Football Scoreboard plugin if not essential to site functionality
• Restrict user roles with posting capabilities to Administrator and Editor levels only
• Implement server-side input validation and output encoding through custom code filters
• Deploy Content Security Policy headers to mitigate the impact of any successful XSS injection

# WordPress configuration - restrict contributor capabilities
# Add to wp-config.php or functions.php to limit shortcode usage

# Example CSP header configuration for Apache (.htaccess)
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';"

# Example CSP header configuration for Nginx
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';";