The error message
Steps for allowing cut, copy, & paste in Firefox
Install the AllowClipboardHelper extension.
Go to https://addons.mozilla.org/en-US/firefox/addon/allowclipboard-helper/ and install the AllowClipboard Helper extension.
Try to edit a webpage on your website.
You’ll see a yellow tab that says Text Cut, Copy & Paste Not Allowed.
Click the yellow tab.
A dialog box will open that lists sites where you allow use of those clipboard buttons. You should see the URL of your website listed.
If you’re feeling nerdy….
If you’re feeling nerdy and you want to learn more about this issue and how to manually deal with it, check out: