This looks promising: https://help.bloxcms.com/knowledge-base/applications/settings/users/authentication_provider/article_fa0ce6ec-9824-11e4-b296-23bd78ef308a.html:
The Authentication Provider option allows your site to serve as an OpenID Authentication Provider. This means that users of your site may use their credentials from your site to log in to other sites that permit it. Other BLOX CMS sites could act as client sites, permitting this exchange of log in credentials.
It should be possible to configure a BLOX CMS site to function as the OpenID Authentication provider for Discourse. If so, this would mean that users could log into your Discourse forum through your TownNews site. To set this up you will need to install the Discourse OpenID Connect on your Discourse site. Configuring it could involve some trial and error. Let us know if you get stuck and we’ll try to help.