How do I know if my Mazolla browser is cloned and someone else is signed in as myself?

An .msi file is a Windows Installer package is a standard file format used by Windows to install software. Because it installs software directly onto your computer, Windows gives you a generic warning (like the one in your photo) just to make sure you trust the source before running it. So if you downloaded this file from the '''official Mozilla page''' you have nothing to fear. If not delete that file and go to https://www.mozilla.org/