User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20171207194519 Steps to reproduce: Calling indexedDB.open doesn't work if the users starts FF with --private. STR: - Install https://addons.mozilla.org/en-US/firefox/addon/youtube-subscription-checker/ - Close Firefox - Launch Firefox with --private - Open the addon's page by clicking on the icon Actual results: The addon fails to open its indexedDB. It shows a screen about DB corruption. Expected results: The addon works normally. Re-launching Firefox without --private and everything will be back to normal. Found this issue from this comment: https://addons.mozilla.org/en-US/firefox/addon/youtube-subscription-checker/reviews/1016623/