Nucleus version 3.24 has been released:
This release fixes a recently discovered cross site scripting issue. While there are no new features in this release, upgrading is recommended when your Nucleus installation has the "Allow Visitors to Create a Member Account" option enabled.
By the way, thanks to the folks at Nucleus for recommending users to upgrade to the new version and not saying that it is a required or mandatory upgrade. I don't know why that gets my goat, but the rebel geek inside of me always resists doing what others think I should be required to do.