The plugin does not sanitize and escape a parameter before outputting it back in the page when importing a CSV, and doe snot have CSRF checks in place as well, leading to a Reflected Cross-Site Scripting.
Create a .txt file and the below line there:
$ echo "<script>alert(/XSS/)</script>"
Make a logged in admin import the file (via "WP CSV" > "Import") to trigger the XSS
The attack could also be performed via CSRF