The Mang Board plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'user_name' parameter in all versions up to, and including, 2.4.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The save-time sanitizer mbw_htmlspecialchars2() is ineffective against this vector because the exploit payload relies solely on unquoted HTML attribute syntax using only spaces, alphanumerics, and characters such as =, parentheses, and dots — none of which are escaped.