Sugarcube 'version' confusion

I like to use the Sugarcube Story Format, but am confused as to 'versions'.

When I select it from the menu in the online version of Twine it says 'Version 1.0.34' but I've seen people on the forum talking about 'Version 2.9.0'

I want to make sure I'm using the latest, but don't see a '2.9.0' option version anywhere??