The Five9 Live Chat plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'toolbar' attribute of the [five9-chat] shortcode in all versions up to, and including, 1.1.2. This is due to insufficient input sanitization and output escaping. 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.
CWE-79