CVE-2021-24159Network attack vector

Stored XSS via forged custom CSS updates

Published Apr 5, 2021 · Updated Aug 3, 2024

Stored XSS in Contact Form 7 Style 3.1.9 and earlier allows remote attackers to inject JavaScript through forged custom CSS updates. The custom CSS handler accepts a forged state-changing request without a nonce check and stores unsanitized input that browsers execute as JavaScript. Exploitation requires an authenticated administrator to open an attacker-controlled link or attachment, after which the stored script can run for site visitors.

CVSS severity8.8
High
EPSS probability0.59%
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 Contact Form 7 Style 3.1.9 and earlier allows remote attackers to inject JavaScript through forged custom CSS updates. The custom CSS handler accepts a forged state-changing request without a nonce check and stores unsanitized input that browsers execute as JavaScript. Exploitation requires an authenticated administrator to open an attacker-controlled link or attachment, after which the stored script can run for site visitors.

The record

CVE
CVE-2021-24159
Published
Apr 5, 2021
Updated
Aug 3, 2024
Vendor
ionuticlanzan
Product
Contact Form 7 Style
Classifications
CWE-352, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 5, 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=3.1.9 <=3.1.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ionuticlanzan · Contact Form 7 Styleversion=3.1.9 <=3.1.9

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-352Cross-Site Request Forgery (CSRF)
T1190Exploit Public-Facing Application

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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