Firefox now allows Web pages to modify the content of clipboard programmatically in user-generated event handlers, so click-to-copy actions, for instance, no longer require an alternative solution like Flash Player. See a relevant thread on the dev-platform list and the Mozilla Hacks blog for details.
This change has updated the implementation of
document.queryCommandEnabled, and those methods no longer throw for the
copy commands, instead return
true in user-generated event handlers or
false in other cases. The
paste command still won’t work for security reasons, and those methods will return
document.queryCommandSupported method now returns a correct value, instead of always returning