On September 6 a security vulnerability affecting all versions of Mozilla Firefox and the Mozilla Suite was reported to Mozilla by Tom Ferris and on September 8th was publicly disclosed.

On September 9, the Mozilla team released a configuration change which, as a temporary measure to work around this problem, disables IDN in the browser. IDN functionality will be restored in a future product update.

1. Type about:config into the address field and hit Enter.
2. In the Filter toolbar, type network.enableIDN.
3. Right click on the the network.enableIDN item and select toggle to change value to false.