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TI-2021-04361 Aliases CVE-2021-21259

Stored XSS in slide mode

Priority LOW 35CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Cross-site scripting
Confidentiality · integrity · availability
None · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

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.

Why it matters now

EPSS 0.01369 72nd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed hedgedoc (hedgedoc): 1.7.2

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
hedgedochedgedocbefore 1.7.21.7.2Patch availableCNA
  • hedgedoc Vendorhedgedoc Affected before 1.7.2 Fixed in 1.7.2 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:hedgedoc:hedgedoc:*:*:*:*:*:*:*:*before 1.7.2Vulnerablehedgedoc
  • cpe:2.3:a:hedgedoc:hedgedoc:*:*:*:*:*:*:*:* Versions before 1.7.2 Vulnerable ·hedgedoc

Remediation

  • Fix · CNA hedgedoc (hedgedoc) Fixed in 1.7.2

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-21259

References

Exploit 1

Patch 1

Advisory 2

  • TI-2023-19867 HedgeDoc API allows to hide existing notes CVSS 3.1HIGH 8.2
  • TI-2024-30379 MySQL & free URL mode allows to hide existing notes in hedgedoc CVSS 3.1MEDIUM 6.5
  • TI-2021-10188 PDF export allows arbitrary file reads CVSS 3.1CRITICAL 10.0
  • TI-2020-16108 Stored XSS in mermaid diagrams CVSS 3.1HIGH 8.7
  • TI-2021-10211 Improper Neutralization of Script-Related HTML Tags in Notes CVSS 3.1HIGH 8.1
  • TI-2021-16561 XSS vector in slide mode speaker-view CVSS 3.1HIGH 8.1
See all 12 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences