dom.event.clipboardevents.enabled lets websites get notifications if the user copies, pastes, or cuts something from a web page, and it lets them know which part of the page had been selected. The emitting of the oncopy, oncut and onpaste events are controlled by this preference.

Values

true (default)
The oncopy, oncut and onpaste events are enabled for web content.
false
The oncopy, oncut and onpaste events are disabled for web content.