FireFox: Holding ctrl+v produces odd cursor behavior and line breaks

[Jude Allred]

1. go to ckeditor.com/demo

2. click 'new page'

3. type 'a'

4. select 'a', press ctrl+c

5. hold ctrl+v

[expected] A continous stream of "a"s are produced

[actual] After a few moments, the cursor resets to the start of the document and begins a fresh line of "a"s.

Note: The start of the broken behavior is inconsistent- sometimes it starts immediately, other times it doesn't occur until dozens of "a"s have been pasted.

See video