CVE-2021-27520Public exploitNetwork attack vector

Browser script execution via reflected author parameter

Published Mar 19, 2021 · Updated Aug 3, 2024

Reflected XSS in FUDForum 3.1.0 allows remote attackers to execute JavaScript in a user's browser through the author search parameter. The index.php search form reflects the author value into generated markup, where an injected quote creates an onmouseover handler. Execution requires a victim to open the crafted search response and hover over the injected value, enabling actions and data access within that victim's forum session.

CVSS severity6.1
Medium
EPSS probability6.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in FUDForum 3.1.0 allows remote attackers to execute JavaScript in a user's browser through the author search parameter. The index.php search form reflects the author value into generated markup, where an injected quote creates an onmouseover handler. Execution requires a victim to open the crafted search response and hover over the injected value, enabling actions and data access within that victim's forum session.

The record

CVE
CVE-2021-27520
Published
Mar 19, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 19, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NVDAV:N/AC:M/Au:N/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
Privilegesunauthenticated
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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