Our servers are fully encrypted and there's no reason to worry about security issues. We use the GA data to show your organic traffic and get more information about your site's backlinks. You can see it in action in our video tour: https://www.youtube.com/watch?v=yrbtumNen2g
Companies from top 100 Alexa are using our tool, and no one has ever had any problems.
However, if you have any concerns, you can add your domain without connecting with GA.