CVE-2021-24637Public exploitNetwork attack vector

Stored script execution via unsanitized block settings

Published Sep 20, 2021 · Updated Aug 3, 2024

Stored XSS in Fonts Plugin before 3.0.3 allows remote authenticated users with Contributor access to execute scripts through Gutenberg blocks. The Gutenberg block accepts blockType, content, align, color, variant, and fontID values and places them into page markup without sufficient sanitization or escaping. A Contributor must save a crafted block and a victim must view the resulting page, where the script runs with access to data and actions available in that visitor's browser session.

CVSS severity5.4
Medium
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Fonts Plugin before 3.0.3 allows remote authenticated users with Contributor access to execute scripts through Gutenberg blocks. The Gutenberg block accepts blockType, content, align, color, variant, and fontID values and places them into page markup without sufficient sanitization or escaping. A Contributor must save a crafted block and a victim must view the resulting page, where the script runs with access to data and actions available in that visitor's browser session.

The record

CVE
CVE-2021-24637
Published
Sep 20, 2021
Updated
Aug 3, 2024
Vendor
Fonts Plugin
Product
Fonts Plugin
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=3.0.3 <3.0.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Fonts Plugin · Fonts Pluginversion=3.0.3 <3.0.3

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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