Some additional info...
Obviously these add-ins have to do what they do by design in order to work. I suppose one could argue that the bug is in the add-ins, but they are working as designed, so either the bug is in FireFox itself, or CE. Either way, CE should somehow prevent any outside code from inserting itself into their editor.
We are going to try some things on our end to see if somehow we can prevent this, but I'm not very optimistic about them working.
Any other solution ideas? Does this need to be brought to the attention of the mozilla people?