Path disclosure security issues enable a malicious user to see the path of the webroot/file: eg: /home/www/etc/public_html.
Combined with other vulnerabilities - like SQL Injection or File Inclusion - a malicious user could use the full path to get the file he wishes to attack.
The problem is located under Wordpress plugin Wordpress Popular Posts on file wordpress-popular-posts.php
Just request the url:
The invalid token will return an error with the full path disclosure:
Notice: Undefined index: token in /home/www/www/nx-wp/wp-content/plugins/wordpress-popular-posts/wordpress-popular-posts.php on line 1248
WPP: Oops, invalid request!
In my opinion it's a low vulnerability because it needs another vulnerability to achieve higher goals.
Just create a filter on the PHP file to not show the PHP Notice or insert it on php.ini. Error, warnings and notices from the server could always be used to find something. Hope it helps.
Brain and Google Inspector