CVE-2023-4021Network attack vector

Stored XSS via unsanitized calendar settings

Published Oct 20, 2023 · Updated Apr 8, 2026

Stored XSS in Webnus Modern Events Calendar Lite before 7.1.0 allows remote authenticated users to execute scripts through calendar settings. The Google API key and Calendar ID settings accept HTML or JavaScript without sufficient input sanitization and later render it without output escaping. Administrator privileges are required, and exposure is limited to multisite installations or sites where unfiltered_html is disabled; injected code runs when a user opens an affected page.

CVSS severity4.4
Medium
EPSS probability0.32%
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 Webnus Modern Events Calendar Lite before 7.1.0 allows remote authenticated users to execute scripts through calendar settings. The Google API key and Calendar ID settings accept HTML or JavaScript without sufficient input sanitization and later render it without output escaping. Administrator privileges are required, and exposure is limited to multisite installations or sites where unfiltered_html is disabled; injected code runs when a user opens an affected page.

The record

CVE
CVE-2023-4021
Published
Oct 20, 2023
Updated
Apr 8, 2026
Vendor
Webnus
Product
Modern Events Calendar Lite
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Oct 20, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 8, 2026Record 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 <7.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Webnus · Modern Events Calendar Liteversion=0 <7.1.0

Published CVSS scores

4.4WordfenceCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:L/I:L/A:N
4.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript

Public exploit references

No public exploit references are available in this record.

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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