Currently there is bugzilla 4.0.2 online, but bugzilla 4.3.1 is the most up-to-date version is 4.0.6 (or even better 4.3.1)
In these versions loads of security issues were fixed and new features were added too. (http://www.bugzilla.org/news/#release402)
As Bugzilla 4.3.1 is unstable branch, please consider update at least to latest stable 4.2.x version, where following nice features are available (amongst other):
- Disabling Old Components, Versions and Milestones
- Improved Searching System
- Local bug IDs are now valid in the See Also field. Adding such an ID will also add a reciprocal link in the other bug.
- Creating an Attachment by Pasting Text Into a Text Field
Demo version with admin rights can be created at http://demo.bugzilla.org/create.cgi
*** Bug 51070 has been marked as a duplicate of this bug. ***
@Rainer: IMHO this bug blocks 51070...
I've upgraded to 4.2.3 now.