Go to a red hat bugzilla page like
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=79752 and click on one of
the past comments (dark grey background). Try to use alt-w or alt-q to close
the window, watch it fail (my meta key is set to alt -- ctrl makes no
difference). This is 7.3 with the latest errata applied.
For reference, this is fixed in the 8.0 mozilla.
Marking fixed based on reporter comments.