Webbläsare
How to reverse / block "allow to paste" in Developer Web Console (Firefox)
In the address bar, type about:config and press Enter/Return.
Proceed to the config / settings options.
In the Search field, type devtools.selfxss.count, then doubleclick this preference (or right-click and choose "Reset")
to set it to the default value of 0 (null).
Restart Firefox. devtools.selfxss.count needs to be 0 when Firefox boots up to get the warning.