The BitForm plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'bitform' shortcode in versions up to, and including, 1.1.0. This is due to insufficient input sanitization and output escaping on user-supplied shortcode attributes ('width' and 'height') in the Shortcode::shortcode() function, which are interpolated directly into the 'style' attribute of an <iframe> element. 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.
https://plugins.trac.wordpress.org/browser/bitform/tags/1.1.0/index.php#L54
https://plugins.trac.wordpress.org/browser/bitform/tags/1.1.0/Common/Shortcode.php#L17
https://plugins.trac.wordpress.org/browser/bitform/tags/1.1.0/Common/Shortcode.php#L13