Just for fun, I downloaded the official LastPass chrome extension. The zip file is 32MB before unzipping, and it has 426 separate *.js files, total of 25MB of javascript. That should be a fun audit.
Edit: To be clear, nobody has said the LastPass extension is compromised, though that is one possibility.
Edit #2: Some of the larger js files do have a fair amount of the size as arrays of localized text, error messages, lists of numbers, etc. But it is still a lot of JS.