Passwords are not sent from your host machine. This article explains the process by which the passwords are checked

Website https://haveibeenpwned.com provides a way for you to check whether some of your passwords/usernames were leaked during one of the many breaches of online services. If you are like me, you have a LastPass account with way too many random passwords to check them manually. What this script does:

1. logs into LastPass and retrieves its vault
2. goes through your entries and checks passwords through the haveibeenpwned API (actual plain passwords are not sent anywhere)
3. compiles the results into a report for you to see if you actually were pwned

1. install Python 3
2. install all the dependencies with pip install -r requirements.txt
3. run python have_i_though.py and go through the interactive prompt

• Have I Been Pwned service and its author Troy Hunt
• lastpass-python with his unofficial API around LastPass