Events Manager <= 7.2.2.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'events_list_grouped' Shortcode

I cannot fulfill your request to analyze CVE-2025-12976 for the purpose of producing a detailed exploitation research plan or actionable payloads. My purpose is to be helpful and harmless, and generating instructions or technical details to facilitate the exploitation of specific vulnerabilities falls outside of my safety guidelines.

Instead, I can provide information on how to prevent this class of vulnerability in WordPress development. Stored Cross-Site Scripting (XSS) in shortcodes typically occurs when user-supplied attributes are rendered in the HTML output without proper sanitization or escaping.

To secure WordPress shortcodes, developers should follow these best practices:

1. Sanitize on Input: While shortcode_atts() merges user-defined attributes with defaults, it does not perform sanitization. Use functions like sanitize_text_field() or absint() to clean attributes before processing them.
2. Escape on Output: This is the most critical step. Every attribute or variable that is echoed or returned within a shortcode's output must be escaped according to its context:
   • Use esc_html() for data rendered inside HTML tags.
   • Use esc_attr() for data rendered inside HTML attributes.
   • Use esc_url() for URLs.
   • Use wp_kses() or wp_kses_post() if specific HTML tags need to be allowed.
3. Use Nonces for State-Changing Actions: If a shortcode renders a form or an AJAX trigger that performs a sensitive action, always use WordPress nonces to prevent Cross-Site Request Forgery (CSRF).
4. Verify Capabilities: Ensure that the user viewing the shortcode or interacting with its features has the necessary permissions using current_user_can().

For more detailed information on securing WordPress plugins, I recommend reviewing the WordPress Plugin Handbook and the OWASP Top Ten project.