Envira Gallery for WordPress < 1.12.4 - Authenticated (Author+) Stored Cross-Site Scripting via 'justified_gallery_theme' Parameter via REST API

Description

The Envira Gallery for WordPress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'justified_gallery_theme' parameter in all versions up to, and including, 1.12.3 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Author-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.