CVE-2026-4076: Slider Bootstrap Carousel XSS Vulnerability

CVE-2026-4076 Overview

The Slider Bootstrap Carousel plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability in the category and template shortcode attributes affecting all versions up to and including 1.0.7. The vulnerability stems from insufficient input sanitization and output escaping on user-supplied shortcode attributes, allowing authenticated attackers with Contributor-level access or above to inject arbitrary web scripts into pages.

Critical Impact

Authenticated attackers can inject malicious JavaScript that executes whenever users access the compromised page, potentially leading to session hijacking, credential theft, or website defacement.

Affected Products

• Slider Bootstrap Carousel plugin for WordPress versions up to and including 1.0.7

Discovery Timeline

• 2026-04-22 - CVE-2026-4076 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-4076

Vulnerability Analysis

This Stored Cross-Site Scripting vulnerability exists in the shortcode processing functionality of the Slider Bootstrap Carousel plugin. The plugin uses extract() on shortcode_atts() to parse user-supplied attributes, which then get directly output into the HTML without proper sanitization. Specifically, the $category variable is rendered into multiple HTML attributes including id, data-target, and href across lines 38, 47, 109, and 113 of the sbc-shortcode.php file without applying WordPress's esc_attr() escaping function. Similarly, the $template attribute flows into a class attribute on line 93 without any escaping.

This pattern creates a persistent XSS condition where malicious JavaScript payloads embedded in these shortcode attributes are stored in the WordPress database and executed in the browsers of all users who view the affected page. The stored nature of this XSS makes it particularly dangerous as the payload persists across sessions and affects all visitors.

Root Cause

The root cause is a failure to implement proper output escaping when rendering user-controlled shortcode attribute values into HTML. WordPress provides built-in escaping functions such as esc_attr() for attribute contexts and esc_html() for HTML content contexts, but the vulnerable code bypasses these security controls by directly outputting the raw $category and $template variables.

The use of PHP's extract() function on shortcode attributes compounds the issue by creating variables directly from user input, making it easier to inadvertently use unsanitized values in output contexts.

Attack Vector

The attack vector requires authentication with at least Contributor-level permissions on the WordPress site. An attacker with this access can create or edit posts/pages containing the vulnerable shortcode with malicious attribute values. When other users (including administrators) view the page containing the malicious shortcode, the injected JavaScript executes in their browser context.

The network-accessible nature of WordPress sites means this vulnerability can be exploited remotely by any authenticated user meeting the minimum privilege requirements, without requiring any user interaction beyond normal page viewing.

Detection Methods for CVE-2026-4076

Indicators of Compromise

• Unusual JavaScript code appearing within slider shortcode attributes in post content
• Posts or pages containing [slider_bootstrap] shortcodes with encoded or obfuscated content in category or template attributes
• Browser console errors or unexpected script executions when viewing pages with slider carousels
• Reports of suspicious redirects or pop-ups on pages containing the slider plugin

Detection Strategies

• Audit WordPress post content for shortcodes containing suspicious payloads in the category or template parameters
• Implement Content Security Policy (CSP) headers to detect and block inline script execution
• Review user accounts with Contributor-level or above access for suspicious activity
• Monitor web application firewall logs for XSS attack patterns targeting WordPress shortcodes

Monitoring Recommendations

• Enable WordPress audit logging to track post and page modifications by contributors
• Configure web application firewall rules to detect common XSS payloads in form submissions
• Regularly scan WordPress database for stored XSS patterns in post content tables
• Monitor browser-based security tools for CSP violations on pages using the slider plugin

How to Mitigate CVE-2026-4076

Immediate Actions Required

• Update the Slider Bootstrap Carousel plugin to a patched version if available
• Audit all existing posts and pages for potentially malicious shortcode attributes
• Review and restrict Contributor-level user accounts until the vulnerability is addressed
• Consider temporarily deactivating the plugin if no patch is available

Patch Information

Monitor the WordPress plugin repository and the Wordfence Vulnerability Analysis for updated patch information. The vulnerability exists in version 1.0.7 and below; check for newer releases that address the input sanitization issues in the plugin source code.

Workarounds

• Temporarily deactivate the Slider Bootstrap Carousel plugin until a security patch is released
• Restrict user roles to prevent untrusted users from having Contributor-level access or above
• Implement a Web Application Firewall (WAF) rule to filter XSS payloads in shortcode parameters
• Manually sanitize existing shortcode instances by reviewing and cleaning the category and template attributes

# Search WordPress database for potentially malicious shortcode content
wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%[slider_bootstrap%category=%' OR post_content LIKE '%[slider_bootstrap%template=%'" --allow-root