The Royal Elementor Addons plugin for WordPress is vulnerable to Stored Cross-Site Scripting via image captions in the Image Grid/Slider/Carousel widget in versions up to and including 1.7.1056. This is due to insufficient output escaping in the render_post_thumbnail() function, where wp_kses_post() is used instead of esc_attr() for the alt attribute context. 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 a page with the malicious image displayed in the media grid widget.