SlimStat Analytics <= 5.3.2 - Unauthenticated Stored Cross-Site Scripting

The SlimStat Analytics plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'outbound_resource' parameter in the slimtrack AJAX action in all versions up to, and including, 5.3.2. This is due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.