Zettlr vulnerable to cross-site scripting


Zettlr provided by Hendrik Erz is a Markdown editor. Zettlr contains a cross-site scripting vulnerability (CWE-79).

Eiji Mori of flatt security Inc. reported this vulnerability to IPA.
JPCERT/CC coordinated with the developer under Information Security Early Warning Partnership.
CVSS Severity (What is CVSS?)

CVSS V3 Severity:
Base Metrics 5.0 (Medium) [IPA Score]
  • Attack Vector: Local
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: Required
  • Scope: Changed
  • Confidentiality Impact: Low
  • Integrity Impact: Low
  • Availability Impact: None
CVSS V2 Severity:
Base Metrics 4.3 (Medium) [IPA Score]
  • Access Vector: Network
  • Access Complexity: Medium
  • Authentication: None
  • Confidentiality Impact: None
  • Integrity Impact: Partial
  • Availability Impact: None
Affected Products

Hendrik Erz
  • Zettlr versions from 0.20.0 to 1.8.8


If a file or code snippet containing an invalid iframe is loaded into Zettlr, an arbitrary script may be executed on the system where it runs.

[Update the Software]
Update the software to the latest version according to the information provided by the developer.
Vendor Information

Hendrik Erz
CWE (What is CWE?)

  1. Cross-site Scripting(CWE-79) [IPA Evaluation]
CVE (What is CVE?)

  1. CVE-2021-20727

  1. JVN : JVN#98239374
  2. National Vulnerability Database (NVD) : CVE-2021-20727
Revision History

  • [2021/05/26]
      Web page was published
  • [2021/05/31]
      Affected Products : Content was modified
      Impact : Content was modified
  • [2021/06/03]
      Vendor Information : Content was added