CVE-2021-39201Network attack vector

Stored XSS via block-editor sanitization bypass

Published Sep 9, 2021 · Updated Aug 4, 2024

Stored cross-site scripting in the WordPress block editor before 5.8 allows remote authenticated users to execute scripts in another user's browser. The editor accepts crafted content from Contributor- or Author-level accounts while bypassing the unfiltered_html restriction; the exact sanitization path is undisclosed. Exploitation requires a low-privileged account and user interaction with the crafted content, exposing or modifying data available to the affected editor session.

CVSS severity5.4
Medium
EPSS probability1.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored cross-site scripting in the WordPress block editor before 5.8 allows remote authenticated users to execute scripts in another user's browser. The editor accepts crafted content from Contributor- or Author-level accounts while bypassing the unfiltered_html restriction; the exact sanitization path is undisclosed. Exploitation requires a low-privileged account and user interaction with the crafted content, exposing or modifying data available to the affected editor session.

The record

CVE
CVE-2021-39201
Published
Sep 9, 2021
Updated
Aug 4, 2024
Vendor
WordPress.org
Product
WordPress
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 9, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 5.0, < 5.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

WordPress.org · WordPressversion=>= 5.0, < 5.8.0

Published CVSS scores

5.4CanonicalCVSS:3.1/AV:N/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

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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