CVE-2025-48877Network attack vector

Iframe-scoped JavaScript execution via default CodePen allowlist

Published Jun 9, 2025 · Updated Jun 9, 2025

Script execution in Discourse stable before 3.4.4 and beta before 3.5.0.beta5 allows remote attackers to run JavaScript in CodePen iframes. The default allowed_iframes setting includes the CodePen prefix, so an accepted embed automatically starts untrusted code within its iframe. The tests-passed branch before 3.5.0.beta6-dev is also affected; execution is confined to the iframe scope, and the placement vector is undisclosed.

CVSS severity9.8
Critical
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Script execution in Discourse stable before 3.4.4 and beta before 3.5.0.beta5 allows remote attackers to run JavaScript in CodePen iframes. The default allowed_iframes setting includes the CodePen prefix, so an accepted embed automatically starts untrusted code within its iframe. The tests-passed branch before 3.5.0.beta6-dev is also affected; execution is confined to the iframe scope, and the placement vector is undisclosed.

The record

CVE
CVE-2025-48877
Published
Jun 9, 2025
Updated
Jun 9, 2025
Vendor
Discourse
Product
Discourse
Classifications
CWE-1038, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 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=< 3.4.4
  2. Affected versionversion=< 3.5.0.beta5
  3. Affected versionversion=< 3.5.0.beta6-dev

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Discourse · Discourseversion=< 3.4.4; version=< 3.5.0.beta5; version=< 3.5.0.beta6-dev

Published CVSS scores

8.1GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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-1038Insecure Automated Optimizations
T1059.007Command and Scripting Interpreter JavaScript

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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