Improper escaping of user input in discourse-calendar

Vulnerability Description

dicourse-calendar is a plugin for the Discourse messaging platform which adds the ability to create a dynamic calendar in the first post of a topic. Improper escaping of event titles could lead to Cross-site Scripting (XSS) within the 'email preview' UI when a site has CSP disabled. Having CSP disabled is a non-default configuration, so the vast majority of sites are unaffected. This problem is resolved in the latest version of the discourse-calendar plugin. Users are advised to upgrade. Users unable to upgrade should ensure CSP is enabled on the forum.

References

• https://github.com/discourse/discourse-calendar/security/advisories/GHSA-3fwj-f6ww-7hr6
• https://github.com/discourse/discourse-calendar/commit/9788310906febb36822d6823d14f1059c39644de
• https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP