What’s Vulnerable › Vulnerabilities

CVE-2023-43658: Improper escaping of user input in discourse-calendar

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-10-16 · updated 2026-06-17
• Weakness: CWE-79

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.

Affected products

• Discourse Calendar: through 2023-10-16

References

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

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