CVE-2021-43827

discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in ` ` tags (e.g. ` ^[footnote] `, the resulting rendered HTML would include a nested ` `, 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 ` ` 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.