CVE-2021-34667Network attack vector

Reflected XSS via unsanitized PHP_SELF path

Published Aug 16, 2021 · Updated May 5, 2025

Reflected XSS in Calendar_plugin 1.0 and earlier allows remote attackers to execute arbitrary web scripts through crafted request paths. calendar.php places the request-controlled $_SERVER['PHP_SELF'] value into generated markup without neutralizing it. A victim must follow a crafted link, after which the script runs in the victim's browser under the affected WordPress site's origin.

CVSS severity6.1
Medium
EPSS probability0.90%
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 Calendar_plugin 1.0 and earlier allows remote attackers to execute arbitrary web scripts through crafted request paths. calendar.php places the request-controlled $_SERVER['PHP_SELF'] value into generated markup without neutralizing it. A victim must follow a crafted link, after which the script runs in the victim's browser under the affected WordPress site's origin.

The record

CVE
CVE-2021-34667
Published
Aug 16, 2021
Updated
May 5, 2025
Vendor
Calendar_plugin
Product
Calendar_plugin
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 16, 2021CVE publishedPublication date reported by the CVE source.
  2. May 5, 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=1.0 <=1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Calendar_plugin · Calendar_pluginversion=1.0 <=1.0

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1WordfenceCVSS: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 exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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