diff --git a/app/scripts/fetch_xulrunner b/app/scripts/fetch_xulrunner
index 30c3a9073d..aa953744f8 100755
--- a/app/scripts/fetch_xulrunner
+++ b/app/scripts/fetch_xulrunner
@@ -148,15 +148,6 @@ function modify_omni {
 	# Continue using app.update.auto in prefs.js on Windows
 	replace_line 'PER_INSTALLATION_PREFS_PLATFORMS = \["win"\]' 'PER_INSTALLATION_PREFS_PLATFORMS = []' modules/UpdateUtils.sys.mjs
 	
-	# Prompt if major update is available instead of installing automatically on restart
-	replace_line 'if \(!updateAuto\) \{' 'if (update.type == "major") {
-      LOG("UpdateService:_selectAndInstallUpdate - prompting because it is a major update");
-      AUSTLMY.pingCheckCode(this._pingSuffix, AUSTLMY.CHK_SHOWPROMPT_PREF);
-      Services.obs.notifyObservers(update, "update-available", "show-prompt");
-      return;
-    }
-    if (!updateAuto) {' modules/UpdateService.sys.mjs
-	
 	# Avoid console warning about resource://gre/modules/FxAccountsCommon.js
 	replace_line 'const logins = this._data.logins;' 'const logins = this._data.logins; if (this._data.logins.length != -1) return;' modules/LoginStore.sys.mjs
 	
@@ -506,70 +497,9 @@ cd xulrunner
 
 if [ $BUILD_MAC == 1 ]; then
 	GECKO_VERSION="$GECKO_VERSION_MAC"
-	DOWNLOAD_URL="https://ftp.mozilla.org/pub/firefox/releases/$GECKO_VERSION"
-	rm -rf Firefox.app
-	
-	if [ -e "Firefox $GECKO_VERSION.app.zip" ]; then
-		echo "Using Firefox $GECKO_VERSION.app.zip"
-		unzip "Firefox $GECKO_VERSION.app.zip"
-	else
-		curl -o Firefox.dmg "$DOWNLOAD_URL/mac/en-US/Firefox%20$GECKO_VERSION.dmg"
-		set +e
-		hdiutil detach -quiet /Volumes/Firefox 2>/dev/null
-		set -e
-		hdiutil attach -quiet Firefox.dmg
-		cp -a /Volumes/Firefox/Firefox.app .
-		# Store local copy of unmodified app
-		zip -r "Firefox $GECKO_VERSION.app.zip" Firefox.app
-		hdiutil detach -quiet /Volumes/Firefox
-	fi
-	
-	# Download custom components (e.g., XUL), as an xz-compressed tarball of the MacOS folder with
-	# custom files in it
-	echo
-	rm -rf MacOS
-	if [ -n "$custom_components_hash_mac" ]; then
-		if [ -e "Firefox $GECKO_VERSION MacOS.zip" ]; then
-			echo "Using Firefox $GECKO_VERSION MacOS.zip"
-			unzip "Firefox $GECKO_VERSION MacOS.zip"
-		else
-			echo "Downloading custom Firefox components"
-			echo
-			curl -o MacOS.tar.xz "${custom_components_url}mac/$custom_components_hash_mac.tar.xz"
-			
-			# Verify hash
-			if [[ "`uname`" = "Darwin" ]]; then
-				shasum="shasum -a 256"
-			else
-				shasum=sha256sum
-			fi
-			echo
-			echo "$custom_components_hash_mac  MacOS.tar.xz" | $shasum -c -
-			echo
-			
-			tar xvf MacOS.tar.xz
-		fi
-		echo
-	fi
-	
 	pushd Firefox.app/Contents/Resources
 	modify_omni mac
 	popd
-	
-	# Replace "FirefoxCP" with "ZoteroCP" for subprocesses ("Isolated Web Content", "Socket Process", "Web Content", etc.)
-	info_plist=Firefox.app/Contents/MacOS/plugin-container.app/Contents/Resources/English.lproj/InfoPlist.strings
-	from=$(get_utf16_chars "FirefoxCP")
-	to=$(get_utf16_chars "ZoteroCP")
-	perl -pi -e "s/$from/$to/" $info_plist
-	# Check for UTF-16 "ZoteroCP"
-	if ! grep -a -q "Z.o.t.e.r.o.C.P." $info_plist; then
-		echo '"ZoteroCP" not found in InfoPlist.strings after replacement'
-		exit 1
-	fi
-	
-	rm -f Firefox.dmg
-	
-	echo $("$SCRIPT_DIR/xulrunner_hash" -p m) > hash-mac
 fi
 
 if [ $BUILD_WIN == 1 ]; then
@@ -709,9 +639,6 @@ if [ $BUILD_WIN == 1 ]; then
 fi
 
 if [ $BUILD_LINUX == 1 ]; then
-	GECKO_VERSION="$GECKO_VERSION_LINUX"
-	DOWNLOAD_URL="https://ftp.mozilla.org/pub/firefox/releases/$GECKO_VERSION"
-	
 	if [[ -n $arch ]]; then
 		arch_list=("$arch")
 	else
@@ -719,33 +646,11 @@ if [ $BUILD_LINUX == 1 ]; then
 	fi
 	for arch in "${arch_list[@]}"; do
 		xdir="firefox-linux-$arch"
-		rm -rf $xdir
-		
-		archived_file="firefox-$GECKO_VERSION-$arch.tar.xz"
-		if [ -e "$archived_file" ]; then
-			echo "Using $archived_file"
-			cp "$archived_file" "firefox-$GECKO_VERSION.tar.xz"
-		else
-			if [ $arch = "arm64" ]; then
-				moz_arch=aarch64
-			else
-				moz_arch=$arch
-			fi
-			curl -O "$DOWNLOAD_URL/linux-$moz_arch/en-US/firefox-$GECKO_VERSION.tar.xz"
-			# Store local copy of unmodified app
-			cp "firefox-$GECKO_VERSION.tar.xz" "$archived_file"
-		fi
-
-		tar xvf firefox-$GECKO_VERSION.tar.xz
-		mv firefox $xdir
 
 		pushd $xdir
 		modify_omni $arch
 		popd
 		
-		rm "firefox-$GECKO_VERSION.tar.xz"
-		
-		echo "$( $SCRIPT_DIR/xulrunner_hash -p l -a "$arch" )" > "hash-linux-${arch}"
 	done
 fi