CVE-2020-18221Public exploitNetwork attack vector

Code execution via formula-rendering iframe injection

Published May 26, 2021 · Updated Aug 4, 2024

Cross-site scripting in Typora 0.9.65 and earlier allows remote attackers to execute code through a crafted mathematical formula. Formula block rendering accepts attacker-controlled SVG and iframe srcdoc markup, allowing nested JavaScript to reach Electron's Node process bindings and spawn a command. Execution requires a user to open or render the crafted document, and the demonstrated payload targets Windows 10.

CVSS severity6.1
Medium
EPSS probability1.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Typora 0.9.65 and earlier allows remote attackers to execute code through a crafted mathematical formula. Formula block rendering accepts attacker-controlled SVG and iframe srcdoc markup, allowing nested JavaScript to reach Electron's Node process bindings and spawn a command. Execution requires a user to open or render the crafted document, and the demonstrated payload targets Windows 10.

The record

CVE
CVE-2020-18221
Published
May 26, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution
T1204.002User Execution: Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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