If
you disable the autofill feature, you'll have to click the LastPass icon in a password field and click your username to fill your saved information.
There's no way to
disable the autofill feature if you're using the integrated password manager in Google Chrome or Microsoft Edge, for example.
Unfortunately, most browser password managers don't allow you to
disable autofill.
In LastPass, you can
disable autofill by clicking the LastPass extension button on your browser toolbar and clicking «Preferences».
But, for now, you can
disable autofill to make yourself more secure.
As a result, you should probably
disable the autofill feature to prevent this from happening.
There is an option to
disable autofill of passwords in Mozilla Firefox's password manager, but it's hidden in about: config.
Chrome does have an option to
disable autofill, but it only disables autofill of data like addresses and phone numbers, not passwords.
However, you can still mitigate some of your risk from these scripts by
disabling autofill in your password manager.
Not exact matches
If you're using another password manager, you should open its preferences and
disable the «
autofill» or «automatically fill» option to ensure your password manager won't leak your personal information.
If you are letting someone else use your iPhone to browse the internet, it might be a good idea to
disable iCloud Keychain's
AutoFill feature temporarily.