The Mesmerize Companion plugin for WordPress is vulnerable to unauthorized access and modification of data due to a missing capability check on the "openPageInCustomizer" and "openPageInDefaultEditor" functions in all versions up to, and including, 1.6.158. This makes it possible for authenticated attackers - with subscriber level access and above, on websites with the Mesmerize theme activated - to mark arbitrary pages as maintainable, wrap their content in custom sections, change page template metadata, and toggle the default editor flag without proper authorization.