The Slider, Gallery, and Carousel by MetaSlider – Image Slider, Video Slider plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'delay' Post Meta Setting in all versions up to, and including, 3.111.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with custom-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The ml-slider custom post type is registered without custom capability restrictions and the ml-slider_settings meta key is unprotected, allowing Author-level users to set the malicious delay value via XML-RPC custom_fields when creating an ml-slider post.