{"id":"CVE-2021-43827","aliases":["EUVD-2021-30707","GHSA-58vr-c56v-qr57"],"status":"published","title":"Inline footnotes wrapped in \u003ca\u003e tags can cause errors in discourse-footnotes","description":"discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `\u003ca\u003e` tags (e.g. `\u003ca\u003e^[footnote]\u003c/a\u003e`, the resulting rendered HTML would include a nested `\u003ca\u003e`, 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 `\u003ca\u003e` 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.","severity":{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00829,"percentile":0.5784,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-755"],"published":"2021-12-14T22:20:09Z","modified":"2026-10-20T10:55:04Z","products":[{"vendor":"discourse","product":"discourse-footnote"},{"vendor":"discourse","product":"discourse_footnote"}],"references":[{"url":"https://github.com/discourse/discourse-footnote/security/advisories/GHSA-58vr-c56v-qr57","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","advisory"]},{"url":"https://github.com/discourse/discourse-footnote/commit/796617e0131277011207541313522cd1946661ab","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix"]}],"sources":{"cve":[{"id":"CVE-2021-43827","title":"Inline footnotes wrapped in \u003ca\u003e tags can cause errors in discourse-footnotes","description":"discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `\u003ca\u003e` tags (e.g. `\u003ca\u003e^[footnote]\u003c/a\u003e`, the resulting rendered HTML would include a nested `\u003ca\u003e`, 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 `\u003ca\u003e` 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.","status":"published","published":"2021-12-14T22:20:09Z","modified":"2024-08-04T04:03:08.963Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna"}],"cwes":["CWE-755"],"updated_at":"2026-11-02T14:32:56.689433Z"}],"euvd":[{"id":"EUVD-2021-30707","description":"discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `\u003ca\u003e` tags (e.g. `\u003ca\u003e^[footnote]\u003c/a\u003e`, the resulting rendered HTML would include a nested `\u003ca\u003e`, 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 `\u003ca\u003e` 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.","status":"published","published":"2021-12-14T22:20:09Z","modified":"2024-08-04T04:03:08Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-03T03:24:13.193734Z"}],"nvd":[{"id":"CVE-2021-43827","description":"discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `\u003ca\u003e` tags (e.g. `\u003ca\u003e^[footnote]\u003c/a\u003e`, the resulting rendered HTML would include a nested `\u003ca\u003e`, 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 `\u003ca\u003e` 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.","status":"published","published":"2021-12-14T23:15:08.02Z","modified":"2026-06-17T04:11:31.367Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"secondary"},{"version":"2.0","score":4,"vector":"AV:N/AC:L/Au:S/C:N/I:N/A:P","level":"medium","assessor":"primary"}],"cwes":["CWE-755"],"updated_at":"2026-11-02T14:07:02.189991Z"}],"osv":[{"id":"CVE-2021-43827","description":"discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `\u003ca\u003e` tags (e.g. `\u003ca\u003e^[footnote]\u003c/a\u003e`, the resulting rendered HTML would include a nested `\u003ca\u003e`, 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 `\u003ca\u003e` 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.","status":"published","published":"2021-12-14T23:15:08.02Z","modified":"2026-10-20T10:55:04.910849122Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T15:44:21.877444Z"}]}}