Important Debian security fix is uploaded to sid http://packages.qa.debian.org/f/firebird2.5/news/20130318T154817Z.html
You can check Firebird 2.5/2.1 packages security status for this bug CVE-2013-2492 on this page
Here you can find the latest stable release Firebird 2.5.2 for all supported Ubuntu releases.
Follow the Firebird 2.5.x guide for usage and installation.
The Firebird Project team is happy to announce that the v2.5.2 release
candidate kits for Linux, Windows and Mac OS X platforms are ready for
Please read the Release Notes for details.
Enjoy the testing and please don’t hesitate to report the found
regressions (if any) to firebird-devel mailing list or in the bug tracker.
You can check what bugs are already fixed in the next version of Firebird and
review the generated changelog
I was interested in the freebsd related building issues
You can follow this guide to use the mix of Debian sid and experimental distro with latest Firebird package
I have tested the new Firebird 2.5 SuperClassic package on Debian sid and wrote the install instructions (Flamerobin and screenshots are included in the mini guide)