discourse-calendar is a discourse plugin which adds the ability to create a dynamic calendar in the first post of a topic. The limit on region value length is too generous. This allows a malicious actor to cause a Discourse instance to use excessive bandwidth and disk space. This issue has been patched in main the main branch. There are no workarounds for this vulnerability. Please upgrade as soon as possible.
https://github.com/discourse/discourse-calendar/security/advisories/GHSA-65f2-9ghp-x8h8