CallRail Phone Call Tracking <= 0.5.2 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode

The CallRail Phone Call Tracking plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'callrail_form' shortcode in versions up to, and including, 0.5.2 due to insufficient input sanitization and output escaping on the 'form_id' user supplied attribute. This makes it possible for authenticated attackers with contributor level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.