The WP BookWidgets plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'bw_link' shortcode in all versions up to, and including, 0.9 due to insufficient input sanitization and output escaping on user supplied attributes. 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://wordpress.org/plugins/wp-bookwidgets
https://plugins.trac.wordpress.org/changeset/3380322/
https://plugins.trac.wordpress.org/browser/wp-bookwidgets/trunk/wp-bookwidgets.php#L163