It's confusing that the LastPass site is claiming only Firefox is impacted. [1] Whereas the security researcher's site (detectify.com) shows the vulnerability running in Chrome. [2]
Furthermore, the current live version on Firefox addons repository is 3.x [3], which the LastPass team claims is not vulnerable. [1]
The Firefox reference is in the second vulnerability discussed in your link 1, and is unrelated to your link 2 and parent submission. That second vulnerability apparently only affected the version 4 line of the Firefox plugin, which is marked beta in the Mozilla repository.