#!/bin/sh
    PROFILEDIR=`mktemp -p /tmp -d tmp-fx-profile.XXXXXX.d`
    mkdir -p $PROFILEDIR/extensions 
    cd ~/.mozilla/firefox/yvwc47i0.default/
    cp extensions/* $PROFILEDIR/extensions/
    cp addons.json extensions.json $PROFILEDIR/
    cp -R browser-extension-data $PROFILEDIR/
    cp cert_override.txt $PROFILEDIR/
    #cp prefs.js $PROFILEDIR/
    echo 'user_pref("devtools.selfxss.count", 10);' > $PROFILEDIR/prefs.js
    cd -
    firefox -profile $PROFILEDIR -no-remote -new-instance
    rm -rf $PROFILEDIR

Created this as a script somewhere in my path. You'd need to change `cd ~/.mozilla/firefox/yvwc47i0.default/` to match what yours is.