Don't worry, there are no security issues.
About privacy, the bot will ask if you want to store your username private (in your own wallet and only a hash is published) or public (details visible in the Byteball DAG).
Here is the official Steemit page: https://steemit.com/steemit/@punqtured/official-byteball-airdrop-to-steemians
More info about Byteball: https://byteball.org/