I keep getting warnings that a lastpass script is slowing the browser (FF Quantum 57.0.2).
Even more problematic is that the tool doesn't always work correctly - it is confused by the facebook login page where you have the option of logging in via an icon which it has retained from logging in to a different account (several people use the same machine in my house). It is similarly confused by the keepa add-on that allows you to track prices for items on amazon - you can be on an amazon page but login to the embedded keepa object on the page and lastpass will then want to update your amazon login with your keepa login details - the same happens on the facebook login page where it wants to update one account with someone elses login details.