Headline
CVE-2023-45147: Arbitrary keys can be added to a topic's custom fields by any user
Discourse is an open source community platform. In affected versions any user can create a topic and add arbitrary custom fields to a topic. The severity of this vulnerability depends on what plugins are installed and how the plugins uses topic custom fields. For a default Discourse installation with the default plugins, this vulnerability has no impact. The problem has been patched in the latest version of Discourse. Users are advised to update to version 3.1.1 if they are on the stable branch or 3.2.0.beta2 if they are on the beta branch. Users unable to upgrade should disable any plugins that access topic custom fields.
Impact
Before this fix, any user can create a topic and add arbitrary custom fields to a topic. The severity of this vulnerability depends on what plugins are installed and how the plugins uses topic custom fields. For a default Discourse installation with the default plugins, this vulnerability has no impact.
Patches
The problem has been patched in the latest version of Discourse.
Workarounds
Again, this depends on what plugins are installed and how plugins are using the topic custom fields. If plugins are using topic custom fields in security sensitive code path, then a temporary workaround is to uninstall those plugins.