The MaxGalleria plugin for WordPress is vulnerable to unauthorized image upload due to a missing capability check on the add_media_library_images_to_gallery function in all versions up to, and including, 6.4.2. This makes it possible for authenticated attackers, with subscriber access or above, to upload arbitrary images to a gallery.
https://plugins.trac.wordpress.org/browser/maxgalleria/trunk/maxgalleria-image-gallery.php#L95