The Shortcodes and extra features for Phlox theme WordPress plugin before 2.10.7 unserializes the content of an imported file, which could lead to PHP object injection when a user imports (intentionally or not) a malicious file and a suitable gadget chain is present on the blog.
https://wpscan.com/vulnerability/08f3ce22-94a0-496a-aaf9-d35b6b0f5bb6