When you use the XSurfLog extension we collect information from the websites you visit including the URL and some security identifiers of the content like the size and type, but not the actual content. We collect these details so we can identify if the website is malicious as well as record it (if logging in your account is turned on). The record is so you have a historical record for compliance and historical references. If you disable logging we don't record it anywhere in our systems, but you still get the security checks.
The general privacy policy is available at:
https://xsurflog.com/privacy_policy.php