iframe < 4.7 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'iframe' Shortcode

Description

The iframe plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the `iframe` shortcode in versions up to, and including, 4.6 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level permission and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This was partially patched in version 4.6 and fully patched in version 4.7.