CVE-2021-3313Public exploitNetwork attack vector

Browser script execution via unencoded stored content

Published May 20, 2021 · Updated Aug 3, 2024

Stored XSS in Plone CMS before 5.2.4 allows remote authenticated users to execute JavaScript when a victim opens crafted content. The fullname field is rendered without output encoding, while uploaded SVG or HTML files retain browser-executable content types. A low-privileged account can store a fullname payload, or an account with upload rights can publish a malicious file; code runs only when another user opens the affected view or file.

CVSS severity5.4
Medium
EPSS probability0.98%
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 Plone CMS before 5.2.4 allows remote authenticated users to execute JavaScript when a victim opens crafted content. The fullname field is rendered without output encoding, while uploaded SVG or HTML files retain browser-executable content types. A low-privileged account can store a fullname payload, or an account with upload rights can publish a malicious file; code runs only when another user opens the affected view or file.

The record

CVE
CVE-2021-3313
Published
May 20, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 20, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

3.5NIST National Vulnerability DatabaseAV:N/AC:M/Au:S/C:N/I:P/A:N
7.6Compass SecurityCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:L
5.4NIST National Vulnerability DatabaseCVSS: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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 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')
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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