The Post Grid, Slider & Carousel Ultimate – with Shortcode, Gutenberg Block & Elementor Widget plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 1.6.7 via deserialization of untrusted input in the outpost_shortcode_metabox_markup function. This makes it possible for authenticated attackers, with contributor-level access and above, to inject a PHP Object. If a POP chain is present via an additional plugin or theme installed on the target system, it could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute code.