Electric Enquiries <= 1.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'button' Shortcode Attribute

The Electric Enquiries plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'button' parameter of the electric-enquiry shortcode in all versions up to, and including, 1.1 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.