CVE-2023-0289Public exploitNetwork attack vector

Stored script execution via unescaped event location

Published Jan 13, 2023 · Updated Apr 7, 2025

Stored XSS in WebCalendar allows remote authenticated users to execute script in another user's browser through a crafted event location. The build_entry_popup function and view_entry.php insert the stored location into HTML without encoding, so calendar views interpret it as markup. Event-editing access is required, and viewing the saved event runs the payload in the viewer's session.

CVSS severity7.6
High
EPSS probability0.53%
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 WebCalendar allows remote authenticated users to execute script in another user's browser through a crafted event location. The build_entry_popup function and view_entry.php insert the stored location into HTML without encoding, so calendar views interpret it as markup. Event-editing access is required, and viewing the saved event runs the payload in the viewer's session.

The record

CVE
CVE-2023-0289
Published
Jan 13, 2023
Updated
Apr 7, 2025
Vendor
Craig Knudsen
Product
WebCalendar
Classifications
CWE-79
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 13, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 7, 2025Record 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=unspecified <master

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Craig Knudsen · WebCalendarversion=unspecified <master

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
7.6huntr.devCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

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.

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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')

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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