The Smart Slider 3 WordPress plugin before 3.5.1.11 unserialises the content of an imported file, which could lead to PHP object injection issues when a user import (intentionally or not) a malicious file, and a suitable gadget chain is present on the site.
https://wpscan.com/vulnerability/2e28a4e7-e7d3-485c-949c-e300e5b66cbd