From MozillaZine Knowledge Base
Instead of manually setting preferences, the AllowClipboard Helper extension manages security policies with a convenient user interface and automates the steps below.
You can also enable clipboard access by creating a security policy for the site in question. There is no built-in interface to do this, so you will need to edit user.js. You can also edit about:config, but due to a bug, you will not see the changes you've made (though they will take effect).
In user.js, add the following lines:
user_pref("capability.policy.policynames", "allowclipboard"); user_pref("capability.policy.allowclipboard.sites", "http://www.example.com"); user_pref("capability.policy.allowclipboard.Clipboard.cutcopy", "allAccess"); user_pref("capability.policy.allowclipboard.Clipboard.paste", "allAccess");
The line with
user_pref("capability.policy.allowclipboard.sites", "http://www.example.com http://www.example.net");
Replace "http://www.example.com" and "http://www.example.net" with sites you wanted to allow clipboard access.
Granting to signed scripts
Occasionally the above will not work, as the scripts that need access may use an alternate method of accessing the clipboard. To grant these privileges, which include clipboard access, to signed scripts, set signed.applets.codebase_principal_support to true via about:config. This is not recommended as you cannot limit which sites have these extra privileges.