From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.5)
Gecko/20041111 Firefox/1.0

Description of problem:
When network.enableIDN is set to false in about:config, IDN lookups
will initially fail.  When Firefox is stopped and restarted, however,
they will work again, even though the network.enableIDN is still set
to false.

See http://www.shmoo.com/idn/ for an example of how this can be used
for phishing.

Version-Release number of selected component (if applicable):
firefox-1.0-2.fc3

How reproducible:
Always

Steps to Reproduce:
1.  Start Mozilla Firefox.
2.  Type "about:config" into the URL bar.
3.  Set network.enableIDN to false.
4.  Visit http://www.shmoo.com/idn/ and click on one of the links;
    lookup will fail (properly).
5.  Close Firefox & restart.
6.  Type "about:config" into URL bar; confirm that network.enableIDN
    is still set to false.
7.  Visit http://www.shmoo.com/idn/ and click on one of the link;
    lookup will succeed.
    

Actual Results:  IDN lookup succeeds, even though network.enableIDN is
set to false.

Expected Results:  IDN lookup should fail.

Additional info: