Snipzr's privacy policy applies to the extension: https://www.snipzr.com/privacy-policy

The extension sends Snipzr only the address you explicitly ask it to shorten (with any campaign tags you type) and the session credential from your Snipzr sign-in, and it talks to no other host. It does not read page contents, does not observe your browsing, and stores your session and last choices in this browser only. Nothing is sold, and nothing is used for anything but creating and reporting on your own links.