Any authenticated Discourse user can create an unlisted topic

Discourse is an open-source discussion platform. In version 2.8.13 and prior on the stable branch and version 2.9.0.beta14 and prior on the beta and tests-passed branches, any authenticated user can create an unlisted topic. These topics, which are not readily available to other users, can take up unnecessary site resources. A patch for this issue is available in the main branch of Discourse. There are no known workarounds available.