Discourse Calendar plugin adds the ability to create a dynamic calendar in the first post of a topic to Discourse. Rendering event names can be susceptible to XSS attacks. This vulnerability only affects sites which have modified or disabled Discourse’s default Content Security Policy. The issue is patched in version 0.5 of the Discourse Calendar plugin.
Discourse Calendar adds the ability to create a dynamic calendar in the first post of a topic on Discourse. Uninvited users are able to gain access to private events by crafting a request to update their attendance. This problem is resolved in commit dfc4fa15f340189f177a1d1ab2cc94ffed3c1190. As a workaround, one may use post visibility to limit access.