CVE-2020-21053Public exploitNetwork attack vector

Reflected XSS via unsanitized navigation query string

Published May 20, 2021 · Updated Aug 4, 2024

Reflected XSS in FusionPBX 4.5.7 allows remote attackers to execute arbitrary JavaScript in an authenticated user's browser via a crafted URL. app/devices/device_imports.php inserts the query_string URL parameter directly into a button's onclick attribute when building a devices.php navigation URL. The attacker needs no FusionPBX account, but an authenticated user must follow the crafted link; execution is confined to that user's web session.

CVSS severity6.1
Medium
EPSS probability0.69%
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 FusionPBX 4.5.7 allows remote attackers to execute arbitrary JavaScript in an authenticated user's browser via a crafted URL. app/devices/device_imports.php inserts the query_string URL parameter directly into a button's onclick attribute when building a devices.php navigation URL. The attacker needs no FusionPBX account, but an authenticated user must follow the crafted link; execution is confined to that user's web session.

The record

CVE
CVE-2020-21053
Published
May 20, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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

4.3NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001Malicious Link

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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