Not that one should have to, but for Firefox you can

    cd .mozilla/firefox/$profile
    git init
    git add extensions
    git commit -am init
    echo '*.xpi diff=zip' >>.gitattributes
    echo '[diff "zip"]' >>.git/config
    echo ' textconv = unzip -c -a' >>.git/config

which at least lets you take a peek at what kind of nefarious updates you're getting.