The bro release notes (https://www.bro.org/sphinx-git/install/release-notes.html) do not mention the addition of the version field to http.log. It was added as of http://github.com/bro/bro/commit/ada2b0088b1173118c616b20e3c31a95f607ac76
Jon
Maybe not relevant anymore since I think it happened between 2.4 and 2.5 ...