I would't enter my passphrase in any online form or on any computer that had internet access.
For sure:
1) Download from Github to a usb stick,
2) Transfer to an offline machine and run it and use values.
3) Wipe machine
My mistake, I forgot to mention it because it was obvious to me. But of course your keys and seeds should NEVER be on an internet connected machine (thats currently on the internet, or later connects to the internet)