The WP Shortcode by MyThemeShop plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'title' parameter of the [tab] shortcode in versions up to, and including, 1.4.17. This is due to insufficient input sanitization and output escaping in the mts_tabs() function, which outputs the title shortcode attribute directly into the HTML output between anchor tags without applying any escaping functions. 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.