ClipMon от anon-kun

To use this addon, simply click the addon's icon to toggle it's activity in a tab.

As of now, there is no option to configure the addons behaviour.
The addon will not monitor your clipboard, if it is not active on any tabs.
If there are tabs where the addon is active, it will automatically append to the page, the content of the clipboard, whenever it is updated.
If a tab where the addon is active, is updated (reloaded etc.), it will automatically deactivate itself on that tab.

The addon appends the clipboard in HTML span elements, with CSS styling setting white-space to pre-wrap.