WP Activity Log <= 5.2.1 - Unauthenticated Stored Cross-Site Scripting via User_id Parameter

The WP Activity Log plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the user_id parameter in all versions up to, and including, 5.2.1 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever an administrative user accesses an injected page.