Update the WordPress YITH WooCommerce Gift Cards Premium plugin to the latest available version (at least 3.20.0).
Dave Jong (Patchstack) discovered and reported this Arbitrary File Upload vulnerability in WordPress YITH WooCommerce Gift Cards Premium Plugin. This could allow a malicious actor to upload any type of file to your website. This can include backdoors which are then executed to gain further access to your website. This vulnerability has been fixed in version 3.20.0.