The blog post included a set of instructions for how users can secure their accounts:
1) Log in to your account and click on 'Your Settings,' then the 'Advanced' tab.
2) At the bottom of the 'Advanced' tab, select 'Reset' next to 'Legacy API key.'
3) Copy down your new API key and change it in all applications. These can include social publishers, share buttons and mobile apps.
4) Go to the 'Profile' tab and reset your password.
5) Disconnect and reconnect any applications that use Bitly. You can check which accounts are connected under the 'Connected Accounts' tab in 'Your Settings.'