LightPress Lightbox < 2.3.5 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'group' Shortcode Attribute

Description

The LightPress Lightbox plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the `group` attribute in the `[gallery]` shortcode in all versions up to, and including, 2.3.4. This is due to the plugin modifying gallery shortcode output to include the `group` attribute value without proper 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.