Confirming a correct User+Pass combination via API?

[simon]

@Richie

I do not need or want to log people in or out of my Discourse itself, I simply need to confirm their user/pass is correct really.

There is no API route that will return a users raw password, so I don’t think this approach is going to work. From your description, it sounds like you want to use Discourse as the SSO provider for your website. That could be made to work. Details about how to set that up are here: Use Discourse as an identity provider (SSO, DiscourseConnect).