Update on LastPass:
LP states in their FAQ that to protect users from phishing attempts at getting their LP master password
"Warning that the master password was entered on a non-LastPass page: LastPass will detect if the user enters their master password on a non-LastPass page and pops a strong warning, even before the user submits it to the page. The user will know immediately that their master password may have been compromised and can change it."
I decided to test this (I highly recommend you do NOT do this yourself) (Also, I specifically changed my master password before doing this so that I could revert to my old password after) by entering my master password on a Gmail log in page. The only "warning" I got was that the LP icon had a small,
barely visible exclamation point added to it, as you can see here:
I did not get any sort of information bar or pop up telling me that something was wrong.
I would not exactly call this a "strong" warning... I have emailed LastPass telling them this and including the screenshot. Will update if/when they respond