I read about this announcement from MozillaZine. The release focuses on minor bugfix on previous Mozilla Firefox release 1.0.4.
The most notable bugfix included in this test build is the spoofable Javascript Dialog Box vulnerability that would lead attacker into tricking and trick the user into entering his/her account information inside the fake password dialog box.
Internet Explorer is also affected by this vulnerability though we havent heard about Microsoft planning to fix it.
You can download Mozilla Firefox test build here :
Windows
Linux