CVE-2023-43658Network attack vector

Stored XSS via unescaped email-preview event titles

Published Oct 16, 2023 · Updated Sep 16, 2024

Stored XSS in Discourse Calendar before 97883109 allows remote authenticated users to execute JavaScript through event titles in email previews. The email formatter in plugin.rb interpolates event_name and dates directly into generated HTML without CGI.escape_html encoding. Exploitation requires a site with CSP disabled, an attacker able to create or edit an event, and a user who opens the affected email preview.

CVSS severity8.0
High
EPSS probability0.50%
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 Discourse Calendar before 97883109 allows remote authenticated users to execute JavaScript through event titles in email previews. The email formatter in plugin.rb interpolates event_name and dates directly into generated HTML without CGI.escape_html encoding. Exploitation requires a site with CSP disabled, an attacker able to create or edit an event, and a user who opens the affected email preview.

The record

CVE
CVE-2023-43658
Published
Oct 16, 2023
Updated
Sep 16, 2024
Vendor
Discourse
Product
Discourse Calendar
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 16, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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 <=9d1726fe
  2. Affected versionversion=< 97883109

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Discourse · Discourse Calendarversion=0 <=9d1726fe; version=< 97883109

Published CVSS scores

8.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
6.1NIST NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
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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