Anything that is free or closed is always risky. It is highly risky if it is both. And blockfolio falls in this category.

You should check out Cointracking Portfolio Manager.

It has

1. Automatic import of trades through APIs.
2. Average purchase and sale price reports.
3. Booked and unbooked profits.
4. Ability to calculate your taxes.
5. Set up price notifications.

For details of how to use these features checkout this post.

It is both paid and open-sourced(may be not full). As in if you pay the full amount you will get the full source code as well.