The key isn't just what software they were using for the forum, but what version of the software. Most sites that get hacked with these scripts are using woefu

The key isn't just what software they were using for the forum, but what version of the software. Most sites that get hacked with these scripts are using woefully outdated versions that have various holes in them, usually because they don't want to have to replace/rewrite modifications or themes. Based on the date, they might have been using a fairly old version of phpBB 3.