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Vulnerability record · public intelligence
CVE-2021-43827
MEDIUM

Inline footnotes wrapped in <a> tags can cause errors in discourse-footnotes

Published Dec 14, 2021 · Updated Oct 23, 2026

Severity · CVSSMEDIUM · 4.3
Known exploitationNot listed
EPSS / likelihood0.83%
QFinch risk scoreNot available

Original summary

Normalized public record · Updated Oct 23, 2026

Inline footnotes wrapped in <a> tags can cause errors in discourse-footnotes

Publisher and source text is retained separately from QFinch interpretation.

QFinch assessment

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.

Evidence: public source records

Affected products

Affected scope reported by the available public evidence
Affected package, product or rangeFix status
Consult the referenced vendor advisory for affected versions.Consult source advisory

Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.

Remediation

Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.

  1. Confirm the affected product and reachable code path exist in your environment.
  2. Apply the vendor-supported patch or mitigation from the primary advisory.
  3. Rescan the exact deployed revision and retain verification evidence.
Review primary references

Evidence coverage

CVENVDEPSS
SSVC priority
LOW
Confidence
Not available
Aliases
None reported

Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.

Sources and record history

  1. Security advisory ↗
  2. Patch commit ↗

Record history

Published Dec 14, 2021 · Last refreshed Oct 23, 2026