WPSite Shortcode <= 1.2 - Authenticated (Contributor+) Stored Cross-Site Scripting

The WPSite Shortcode plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'format' shortcode attribute in the wpsite_y shortcode and the 'before' attribute in the wpsite_postauthor shortcode in all versions up to, and including, 1.2. This is due to insufficient input sanitization and output escaping in error messages. 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.