Install latest stable binary version of firefox for desktop linux distro (tested Debian 11, proably Ubuntu too)

install-firefox-release.sh

#!/usr/bin/env bash
# Purpose: Download and install latest stable firefox for any Linux distribution
# gpg --receive-keys 0x4360FE2109C49763186F8E21EBE41E90F6F12F6D
# Update 2021-06-03: key change, new key is signed with old 0x14F26682D0916CDD81E37B6D61B7B526D98F0353
# https://blog.mozilla.org/security/2021/06/02/updating-gpg-key-for-signing-firefox-releases/

# GPG SETTINGS
RELEASE_KEY_FINGERPRINT="0xADD7079479700DCADFDD5337E36D3B13F3D93274"
MOZILLA_KEY_SERVER="gpg.mozilla.org"
GNUPGHOME="/var/cache/gnupg_download_firefox_release"
MOZILLA_KEY_URL="https://archive.mozilla.org/pub/firefox/releases/114.0b4/KEY"

# FIREFOX VERSION SELECTION
MOZILLA_LATEST_URL="https://product-details.mozilla.org/1.0/firefox_versions.json"
FIREFOX_TARGET_BRANCH="LATEST_FIREFOX_VERSION"

# INSTALL SETTINGS
MOZILLA_BASE_URL_DOWNLOAD="https://ftp.mozilla.org/pub/firefox/releases"
DL_PATH="/var/cache/download_firefox_release"
INSTALL_PATH="/opt/firefox_release"
DL_USER="nobody"

if [ "$(id -u)" -ne 0 ];then
  echo "This script need root privileges"
  exit 1
fi

for TOOL in gpg sudo jq curl wget
do
  if [ ! -x "$(command -v "${TOOL}")" ];then
    echo "Command ${TOOL} not found, please install it or add it in your PATH"
    exit 1
  fi
done


set -euxo pipefail

# clean config vars
INSTALL_PATH="${INSTALL_PATH%/}"
DL_PATH="${DL_PATH%/}"
GNUPGHOME="${GNUPGHOME%/}"

# Setup DL dir
mkdir -p "${DL_PATH}"
chmod 1777 "${DL_PATH}"
cd "${DL_PATH}"


# Setup a GNU PGP home to validate signature from Mozilla
mkdir -p "${GNUPGHOME}"
chmod 700 "${GNUPGHOME}"

function get_key_via_file {
  # DL the key file, import it in a TMP keyring and then export key right
  # key based on the fingerprint so in the final keyring we will have a valid KEY
  cd "${DL_PATH}"
	sudo -u "${DL_USER}" -- wget --no-hsts "${MOZILLA_KEY_URL}" -O "MOZ_KEY.asc"
  sudo -u "${DL_USER}" -- mkdir -p "${DL_PATH%/}/tmpgpghome"
  sudo -u "${DL_USER}" -- gpg --homedir "${DL_PATH%/}/tmpgpghome" \
    --no-default-keyring --keyring tmpkeyring \
    --import MOZ_KEY.asc
  sudo -u "${DL_USER}" -- gpg --homedir "${DL_PATH%/}/tmpgpghome" \
    --no-default-keyring --keyring tmpkeyring \
    --armor --export --output "${DL_PATH%/}/VALID_MOZ_KEY.asc" "${RELEASE_KEY_FINGERPRINT}"
  # Import the trusted key in our keyring
  gpg --homedir "${GNUPGHOME}" --import "${DL_PATH%/}/VALID_MOZ_KEY.asc"
}

if ! gpg --homedir "${GNUPGHOME}" --with-fingerprint -k "${RELEASE_KEY_FINGERPRINT}";then
  get_key_via_file || gpg --homedir "${GNUPGHOME}" \
    --keyserver "${MOZILLA_KEY_SERVER}" --receive-keys "${RELEASE_KEY_FINGERPRINT}"
	# display downloaded key
	gpg --homedir "${GNUPGHOME}" --with-fingerprint -k "${RELEASE_KEY_FINGERPRINT}"
fi

# fetch latest version available on Moz' api
VERSION=$(sudo -u "${DL_USER}" -- curl --fail -s "${MOZILLA_LATEST_URL}" \
  |sudo -u "${DL_USER}" -- jq ".${FIREFOX_TARGET_BRANCH}" -r\
  |head -n 1)

if ! echo "${VERSION}" |grep -P '^[0-9A-Za-z.]{3,16}$' > /dev/null;then
  echo "Invalid version returned by Mozilla API : [${VERSION}]"
  exit 1
fi

if grep "${VERSION}" "${DL_PATH}/installed_version" ;then
  set +x
  echo ""
  echo "Firefox version ${VERSION} already installed"
  echo "purge ${DL_PATH}/installed_version  for reinstall"
  exit 0
fi

FFARCHIVE="firefox-${VERSION}.tar.bz2"

FFARCHIVE_STATUS=0
function verify_ffarchive() {
  if [ -f "${FFARCHIVE}" ];then
    CHECKSUM=$(sha512sum "${FFARCHIVE}"|awk '{print $1}')
    if grep "${CHECKSUM}" "SHA512SUMS" >/dev/null ;then
      FFARCHIVE_STATUS=1
    fi
  fi
}

FFARCHIVE_STATUS=0
verify_ffarchive
if [ ${FFARCHIVE_STATUS} -ne 1 ];then
	sudo -u "${DL_USER}" -- wget --no-hsts "${MOZILLA_BASE_URL_DOWNLOAD}/${VERSION}/SHA512SUMS" -O "SHA512SUMS"
	sudo -u "${DL_USER}" -- wget --no-hsts "${MOZILLA_BASE_URL_DOWNLOAD}/${VERSION}/SHA512SUMS.asc" -O "SHA512SUMS.asc"
	gpg --homedir "${GNUPGHOME}" --verify SHA512SUMS.asc SHA512SUMS
	sudo -u "${DL_USER}" -- wget --no-hsts "${MOZILLA_BASE_URL_DOWNLOAD}/${VERSION}/linux-x86_64/en-US/${FFARCHIVE}" -O "${FFARCHIVE}"
fi

FFARCHIVE_STATUS=0
verify_ffarchive
if [ ${FFARCHIVE_STATUS} -ne 1 ];then
	echo "Invalid checksum  / archive : ${CHECKSUM}"
	rm -f -- "${FFARCHIVE}*"
	exit 1
fi

mkdir -p "${INSTALL_PATH}"
rm -rf -- "${INSTALL_PATH:?}/*" ||true
tar -C "${INSTALL_PATH}/" -jxvf "${FFARCHIVE}"

# remove internal extension (untrusted)
find "${INSTALL_PATH}/firefox/browser/features/" -type f -iname '*.xpi' -print -delete

echo "${VERSION}" > "${DL_PATH}/installed_version"

# clean cache, keep the last for fast re-install
ls -t -- firefox-*.tar.bz2* |awk 'NR > 1'|while read -r ar ; do rm -f -- "${ar}";done;

# Install shortcurt /  .desktop entries
# The profile manger desktop entry
cat > /usr/share/applications/firefox-release-profile-manager.desktop <<EOF
[Desktop Entry]
Name=FF-Release-ProfileManager
Comment=Latest stable Firefox start ProfileManager
GenericName=Web Browser
X-GNOME-FullName=FF-Release-ProfileManager
Exec=${INSTALL_PATH}/firefox/firefox --ProfileManager --no-remote
Terminal=false
X-MultipleArgs=false
Type=Application
Icon=${INSTALL_PATH}/firefox/browser/chrome/icons/default/default128.png
Categories=Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/vnd.mozilla.xul+xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;
StartupWMClass=Firefox
StartupNotify=true
EOF

# The default profile desktop entry
cat > /usr/share/applications/firefox-release-default.desktop <<EOF
[Desktop Entry]
Name=FF-Release-Default
Comment=Latest stable Firefox start current profile
GenericName=Web Browser
X-GNOME-FullName=FF-Release-Default
Exec=${INSTALL_PATH}/firefox/firefox --no-remote
Terminal=false
X-MultipleArgs=false
Type=Application
Icon=${INSTALL_PATH}/firefox/browser/chrome/icons/default/default128.png
Categories=Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/vnd.mozilla.xul+xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;
StartupWMClass=Firefox
StartupNotify=true
EOF

set +x
echo "Firefox ${VERSION} sucessfully installed in ${INSTALL_PATH}"
exit 0

Updated Moz's GPG key
https://blog.mozilla.org/security/2023/05/11/updated-gpg-key-for-signing-firefox-releases/