From 11:10 UTC 02/02/2017 until 22:21 UTC 03/02/2017 users who tried to post, create new topics or use some administration features were getting a 403 error. This was due to CSRF tokens being invalidated after we flushed Discourse’s cache. The issue has since been fixed and the site should be working normally.
We are currently working on extending our monitoring infrastructure to detect these types of issues quicker and in turn resolve them quicker.
If you have any questions/comments, 
