LearnPress <= 4.3.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'skin' Shortcode Attribute

The LearnPress – WordPress LMS Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'skin' attribute of the learn_press_courses shortcode in all versions up to and including 4.3.3. This is due to insufficient input sanitization and output escaping on the 'skin' shortcode attribute. The attribute value is used directly in an sprintf() call that generates HTML (class attribute and data-layout attribute) without any esc_attr() 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.