CVE-2021-4252Network attack vector

Administrator-session script execution via unescaped User-Agent

Published Dec 18, 2022 · Updated Apr 15, 2025

Cross-site scripting in WP-Ban allows remote attackers to run script in an administrator’s browser through a crafted User-Agent header. The toggle_checkbox function in ban-options.php writes HTTP_USER_AGENT directly into the settings page without HTML escaping. The payload executes only when an authenticated administrator opens that page, allowing actions within that administrator’s browser session but not direct server-side code execution.

CVSS severity6.1
Medium
EPSS probability0.46%
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 WP-Ban allows remote attackers to run script in an administrator’s browser through a crafted User-Agent header. The toggle_checkbox function in ban-options.php writes HTTP_USER_AGENT directly into the settings page without HTML escaping. The payload executes only when an authenticated administrator opens that page, allowing actions within that administrator’s browser session but not direct server-side code execution.

The record

CVE
CVE-2021-4252
Published
Dec 18, 2022
Updated
Apr 15, 2025
Vendor
Lester Chan
Product
WP-Ban
Classifications
CWE-707, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2025Record 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=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Lester Chan · WP-Banversion=n/a

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
3.5VulDBCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/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.

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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-707Improper Neutralization
T1059.007JavaScript/JScript

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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