open "about:config" in firefox (type it in the webadress line and hit enter)
  accept the risk in the pop up
  type "clipboard" in the search line
  change the following settings (as shown in the image attachment) from false to true (klick on false)
  restart firefox (close it & open it again)"

The makers of the Avada theme for WordPress adviced to set dom.events.testing.asyncClipboard to true for the copy paste function between sites. A function they have added recently. However, here https://support.mozilla.org/en-US/questions/1411533 I saw this comment: "Recommendations to flip dom.events.testing.asyncClipboard to true are a fundamentally bad idea. This pref was meant for automated testing, and bypasses all security/permission checks on clipboard access. If you toggle this pref, any site has full access to your clipboard all the time without asking you or you even noticing so we suggest that you do not touch that pref. Had the same problem with firefox and outlook web. My solution was: open "about:config" in firefox (type it in the webadress line and hit enter) accept the risk in the pop up type "clipboard" in the search line change the following settings (as shown in the image attachment) from false to true (klick on false) restart firefox (close it & open it again)" The image attachment mentioned, showed that dom.events.testing.asyncClipboard WAS set to true. So now I am confused :-D. Is it dangerous to set it true and why?