By dataI guess you mean tokensrights ?
Since all the data is public on the blockchain. The only thing your account has is the rights to move the tokens in your wallet. Nothing else can be stolen.
For this application, the authentication and security layer is handled by SteemConnect. The application never handles any of your keys. Instead, it receives a token (which remains in your browser) that has a given level of priviledges.
Since the application only receives the rights to vote/comment and follow/unfollow/mute users. That is the maximal risk exposure you take. Of course, you can -- at any time -- decide to revoke the access to the app using the SteemConnect dashboard (available in the top-left menu of the app).
Thanks for your explanation. It makes me satisfied. Just want to make sure it is safe and work like any other.