CVE-2021-43827

discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `<a>` tags (e.g. `<a>^[footnote]</a>`, the resulting rendered HTML would include a nested `<a>`, which is stripped by Nokogiri because it is not valid. This then caused a javascript error on topic pages because we were looking for an `<a>` element inside the footnote reference span and getting its ID, and because it did not exist we got a null reference error in javascript. Users are advised to update to version 0.2. As a workaround editing offending posts from the rails console or the database console for self-hosters, or disabling the plugin in the admin panel can mitigate this issue.

• CWE-755

• https://github.com/discourse/discourse-footnote/commit/796617e0131277011207541313522cd1946661abPatch, Third Party Advisory
• https://github.com/discourse/discourse-footnote/security/advisories/GHSA-58vr-c56v-qr57Third Party Advisory
• https://github.com/discourse/discourse-footnote/commit/796617e0131277011207541313522cd1946661abPatch, Third Party Advisory
• https://github.com/discourse/discourse-footnote/security/advisories/GHSA-58vr-c56v-qr57Third Party Advisory

Published

Dec 14, 2021

Last Modified

Jun 17, 2026

Status

Modified

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