Internal events accidentally exposed to content, including DOMWindowClosed, have been removed


Categories: DOM

Releases: Firefox 79


A Firefox developer noticed that more than a dozen of non-standard, internal events had been exposed to the web, mostly accidentally, but some were for testing purposes. As of Firefox 79, these events are no longer available to web content:

  • DOMWindowClose: Fired when a new tab or popup window was about to be closed with window.close()
  • fullscreen: Not to be confused with fullscreenchange
  • MozBeforeInitialXULLayout
  • MozMouseScrollFailed
  • MozMouseScrollTransactionTimeout
  • MozPaintWait
  • MozPaintWaitFinished
  • MozPerformDelayedBlur
  • occlusionstatechange
  • resolutionchange
  • willenterfullscreen
  • willexitfullscreen
  • XULAlertClose

How can I test this?

This change can be tested with the compatibilty checker in our Firefox Developer Tools extension. Get it today!