{"cve":"CVE-2021-21259","nvd":{"published":"2021-01-22T17:15:12.867","modified":"2026-06-17T03:35:08.637","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","score":6.1},"cwes":["CWE-79"],"references":["https://github.com/hackmdio/codimd/issues/1648","https://github.com/hedgedoc/hedgedoc/commit/35b0d39a12aa35f27fba8c1f50b1886706e7efef","https://github.com/hedgedoc/hedgedoc/releases/tag/1.7.2","https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-44w9-vm8p-3cxw","https://github.com/hackmdio/codimd/issues/1648"],"products":["hedgedoc:hedgedoc"],"source":"nvd","synced_at":"2026-10-19T21:14:10.479542811+00:00"},"epss":{"cve":"CVE-2021-21259","score":0.01369,"percentile":0.71885,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}