CVE-2021-24782Public exploitNetwork attack vector

Stored XSS via unescaped font class name

Published Dec 13, 2021 · Updated Aug 3, 2024

Stored XSS in KP Flex Local Fonts 1.0.0 and earlier allows remote authenticated users to execute JavaScript through a font class name. The Add Font workflow saves the Class Name field without output escaping and renders it on the plugin settings page, where the payload executes. Administrator-level access is required to add a font, and a user must load the settings page; the resulting script runs in that visitor's browser.

CVSS severity4.8
Medium
EPSS probability0.60%
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 KP Flex Local Fonts 1.0.0 and earlier allows remote authenticated users to execute JavaScript through a font class name. The Add Font workflow saves the Class Name field without output escaping and renders it on the plugin settings page, where the payload executes. Administrator-level access is required to add a font, and a user must load the settings page; the resulting script runs in that visitor's browser.

The record

CVE
CVE-2021-24782
Published
Dec 13, 2021
Updated
Aug 3, 2024
Vendor
KP
Product
Flex Local Fonts
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Dec 13, 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=1.0.0 <=1.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

KP · Flex Local Fontsversion=1.0.0 <=1.0.0

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
4.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

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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