The Product Carousel Slider & Grid Ultimate plugin for WordPress is not safe to use. It has a vulnerability called PHP Object Injection in all versions up to 1.9.7. This means that if someone with contributor access or higher uses a certain code, they can inject a PHP Object which can cause harm. If there is another plugin or theme installed on the website that also has a vulnerability, the attacker could delete files, get important information, or even run their own code.