WP Ultimate CSV Importer < 6.5.3 - Admin+ Blind SSRF

The plugin does not fully validate the file to be imported via an URL before making an HTTP request to it, which could allow high privilege users such as admin to perform Blind SSRF attacks

PoC

Put an internal/LAN URL such as below in the file upload by URL function https://127.0.0.1:8080 http://192.168.0.224:8181/?u=https://docs.google.com/