The <graph> tag has just been upgraded to Vega 2.0, adding interactivity support. See live examples here https://www.mediawiki.org/wiki/Extension:Graph/Demo.
Vega 1.0 is still available, but it is obsolete. Please migrate all your graphs to the new system so we can turn 1.0 off. See how to migrate: https://github.com/vega/vega/wiki/Upgrading-to-2.0
Unless the graph definition contains a "version" value, the default is still 1. After I tag all existing graphs, I will switch the default to version 2.
See Vega main page for more: http://vega.github.io/vega/