Many changes to private browsing code of Firefox happened since 17esr out
https://developer.mozilla.org/en-US/docs/Updating_addons_broken_by_private_browsing_changes
Torbutton will be broken by Firefox24ESR private browsing changes.
https://developer.mozilla.org/en-US/docs/Updating_addons_broken_by_private_browsing_changes
Torbutton will be broken by Firefox24ESR private browsing changes.