Need Permission for Firefox Update?!

One thing you could try is to use the root account to do the install. Do not download the app in root do that in a restricted user. Do not browse or leave your internet connection on in root.
To enable root open the utilities app, Directory Utiliy. Open the little lock by entering an admin password. Be sure to disable root through the same menu in DU after the job is done. If you have not enabled root before you can do it by using the password re -set utility in a boot from the OS install DVD. DSo the same if you have forgotten the root password you set.
If you are wary of root you could try the install by putting the Firefox dmg file into the shared user folder, log into an admin user as against just authenticating from a restricted user with an admin PW. Open and mount the dmg file in 'shared' from the admin. I assume it is Firefox in you Mac OS and not Firefox in Windows on an intel partition.
Last thing is try an install just after a restart. If this or anyone else's post sorts it, please close the query by marking it solved.

if you are doing it from an admin account you should have full read+write privileges to the Applications folder which is all that's needed here.

check that this folder has read+write for the admin group.

to make sure open terminal and run

*sudo chgrp -R admin /Applications*

and

*sudo chmod -R 775 /Applications*

*sudo chmod -R 775 /Applications*

No no no NO! That's not right. That will make every single file in /Applications executable. This includes component parts of apps that should not be executable, which could be a security risk. Disk Utility's Repair Permissions will have a field day fixing everything if this command is run.

A better way is to do it is this:

sudo chown -R root:admin /Applications
sudo chmod -R +rX /Applications
sudo chmod -R ug+w /Applications

That will make everything group writeable by admin, and it will ensure that files that shouldn't have the executable bit set, don't.

Probably what happened is that you originally installed Firefox from one user account, and are now running it from another. Even if the account you are running in now is an admin account, it might not have write permission to Firefox.

I'd just trash the old Firefox app and replace it with a fresh new download. That should take care of it.

what kind of a security risk could it possibly be that didn't exist before? please give me a scenario. only root and admin have write rights to those files. making, say, a plist inside one of the packages executable will certainly have no effect on what you can do with it whatsoever. everything else should be and is executable anyway.