CVE-2021-24571Public exploitNetwork attack vector

Stored script execution via unescaped quiz answers

Published Aug 23, 2021 · Updated Aug 3, 2024

Stored cross-site scripting in Harmonic Design HD Quiz before 1.8.4 allows remote authenticated users to execute scripts in visitors' browsers. A Multiple Choice: Text answer is written into an HTML attribute without output escaping, so a crafted answer can inject autofocus and onfocus handlers when the quiz is rendered. Quiz-editing access is required to store the payload, and a visitor must view a page containing the embedded quiz for the script to run.

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

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Stored cross-site scripting in Harmonic Design HD Quiz before 1.8.4 allows remote authenticated users to execute scripts in visitors' browsers. A Multiple Choice: Text answer is written into an HTML attribute without output escaping, so a crafted answer can inject autofocus and onfocus handlers when the quiz is rendered. Quiz-editing access is required to store the payload, and a visitor must view a page containing the embedded quiz for the script to run.

The record

CVE
CVE-2021-24571
Published
Aug 23, 2021
Updated
Aug 3, 2024
Vendor
Harmonic Design
Product
HD Quiz
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 23, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.8.4 <1.8.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Harmonic Design · HD Quizversion=1.8.4 <1.8.4

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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')
T1059.007Command and Scripting Interpreter: JavaScript

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo