The Coachific Shortcode plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'userhash' shortcode attribute in all versions up to and including 1.0. This is due to insufficient input sanitization and output escaping. The plugin uses sanitize_text_field() on the 'userhash' parameter, which strips HTML tags but does not escape characters significant in a JavaScript string context (such as double quotes, semicolons, and parentheses). The sanitized value is then directly interpolated into a JavaScript string within a <script> tag on line 29 without any JavaScript-specific escaping (e.g., wp_json_encode() or esc_js()). 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.