CVE-2021-37695Network attack vector

Authenticated JavaScript execution via unfiltered fake-object HTML

Published Aug 12, 2021 · Updated Aug 4, 2024

Cross-site scripting in CKSource CKEditor 4 before 4.16.2 allows remote authenticated users to execute JavaScript via malformed HTML. The Fake Objects plugin decodes data-cke-realelement content and recreates it without first applying the editor's active content filter. The attacker must submit content through an affected plugin, and another user must load the resulting fake object in a browser.

CVSS severity7.3
High
EPSS probability1.32%
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 CKSource CKEditor 4 before 4.16.2 allows remote authenticated users to execute JavaScript via malformed HTML. The Fake Objects plugin decodes data-cke-realelement content and recreates it without first applying the editor's active content filter. The attacker must submit content through an affected plugin, and another user must load the resulting fake object in a browser.

The record

CVE
CVE-2021-37695
Published
Aug 12, 2021
Updated
Aug 4, 2024
Vendor
CKSource
Product
CKEditor 4
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 12, 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=< 4.16.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

CKSource · CKEditor 4version=< 4.16.2

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
7.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/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')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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