CVE-2021-43827
Expert Analysis
Professional remediation guidance
Get tailored security recommendations from our analyst team for CVE-2021-43827. We'll provide specific mitigation strategies based on your environment and risk profile.
CVSS Score
V3.1EPSS Score
v2025.03.14There is a 0.3% chance that this vulnerability will be exploited in the wild within the next 30 days.
Attack Vector Metrics
Impact Metrics
Description
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.