zurdo said

i need to disable the function from copy paste on the browser.

Hello zurdo,

Would you try this  :

Type in the address bar about:config and press Enter (promise to be careful, if asked)

Type in the search bar and look for the preference :

dom.event.clipboardevents.enabled

and set its value to false

Then close and restart Firefox.

'Hope that will work for you ....

Also see :

http://blog.rabin.io/quick-tip/how-to-disable-copy-paste-protection-on-websites-forms

Are you actually using Firefox 10? PLEASE update to Firefox 64.0.2 Immediately. Download it from www.getfirefox.com ASAP.

If not, please reset your user agent. How to reset the default user agent on Firefox

Is this about copying data from web pages or do you want to disable these function elsewhere?

You can't disable copy and paste functions in Firefox.