CVE-2021-24837Public exploitNetwork attack vector

Stored XSS via unescaped shortcode area parameter

Published Jan 23, 2023 · Updated Aug 3, 2024

Stored XSS in Patrick Posner Passster before 3.5.5.8 allows remote authenticated users to inject scripts through a shortcode. The shortcode renderer inserts the user-controlled area attribute into generated page markup without output escaping, leaving executable markup stored in the post. Contributor access is sufficient, and the script runs when a user opens the affected page, enabling actions in that user's browser context.

CVSS severity5.4
Medium
EPSS probability0.39%
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 Patrick Posner Passster before 3.5.5.8 allows remote authenticated users to inject scripts through a shortcode. The shortcode renderer inserts the user-controlled area attribute into generated page markup without output escaping, leaving executable markup stored in the post. Contributor access is sufficient, and the script runs when a user opens the affected page, enabling actions in that user's browser context.

The record

CVE
CVE-2021-24837
Published
Jan 23, 2023
Updated
Aug 3, 2024
Vendor
Patrick Posner
Product
Passster
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 23, 2023CVE 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=0 <3.5.5.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Patrick Posner · Passsterversion=0 <3.5.5.8

Published CVSS scores

6.4WordfenceCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
5.4NVDCVSS: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-79Cross-Site Scripting (XSS)
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

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Your stack

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