{"id":"CVE-2021-21259","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-21259","generatedAt":"2026-10-27T22:27:54.744Z","title":"In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode.","description":"HedgeDoc is open source software which lets you create real-time collaborative markdown notes. In HedgeDoc before version 1.7.2, an attacker can inject arbitrary JavaScript into a HedgeDoc note, which is executed when the note is viewed in slide mode. Depending on the configuration of the instance, the attacker may not need authentication to create or edit notes. The problem is patched in HedgeDoc 1.7.2. As a workaround, disallow loading JavaScript from 3rd party sites using the `Content-Security-Policy` header. Note that this will break some embedded content.","published":"2021-01-22T17:15:13.000Z","lastModified":"2026-06-17T03:35:09.000Z","status":"Modified","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"cwe":["CWE-79"],"affected":["hedgedoc/hedgedoc"],"epss":{"score":0.01369,"percentile":0.71689,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (1.37%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://github.com/hackmdio/codimd/issues/1648","tags":["Exploit","Patch","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/hedgedoc/hedgedoc/commit/35b0d39a12aa35f27fba8c1f50b1886706e7efef","tags":["Patch","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/hedgedoc/hedgedoc/releases/tag/1.7.2","tags":["Release Notes","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-44w9-vm8p-3cxw","tags":["Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/hackmdio/codimd/issues/1648","tags":["Exploit","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/hedgedoc/hedgedoc/commit/35b0d39a12aa35f27fba8c1f50b1886706e7efef","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/hedgedoc/hedgedoc/releases/tag/1.7.2","tags":["Release Notes","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-44w9-vm8p-3cxw","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-21259","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}