The Waiting: One-click countdowns plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Countdown name in versions up to, and including, 0.6.2 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level permissions 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/waiting/trunk/waiting.php?rev=2826039