You might see this message when you are using an app like CleanMyMac with the option to clean Universal Binaries. This process strips part of Notebooks‘ binary, so Notebooks has the impression that the app has been tampered with. – Yes, we pay attention to this 😉

To resolve this issue we recommend to
  • download and install Notebooks from our website again and
  • turn off the option to clean universal binaries in CleanMyMac.
“Notebooks has been Compromised” – What has Happened?