The message may mean that you got the file

by macnerd10 - 1/20/12 4:29 PM

In Reply to: need a firefox download for macbook pro? by Pinkbaby76

from an untrusted site or that the computer treats a dmg file as suspicious because it contains an installable program. To get it from the real source, go to Mozilla site (http://www.mozilla.org/en-US/firefox/all.html) and download form there. If the message comes back, I would disregard it.