Knowledge Base <= 2.1.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via Block

The Knowledge Base plugin for WordPress is vulnerable to Stored Cross-Site Scripting via div classes that can be added to blocks in versions up to, and including, 2.1.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers with contributor level permissions and above to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.