CVE-2023-3746Public exploitNetwork attack vector

Contributor-level stored XSS via unsanitized post content

Published Oct 16, 2023 · Updated Apr 23, 2025

Stored XSS in Automattic ActivityPub before 1.0.0 allows remote authenticated users to execute script through crafted post content. The plugin preserves a crafted HTML class attribute containing an onerror handler, which executes when the post is viewed or previewed. Contributor access is required to store the payload, and a viewer must open or preview the post for execution in that viewer's browser context.

CVSS severity5.4
Medium
EPSS probability0.40%
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 Automattic ActivityPub before 1.0.0 allows remote authenticated users to execute script through crafted post content. The plugin preserves a crafted HTML class attribute containing an onerror handler, which executes when the post is viewed or previewed. Contributor access is required to store the payload, and a viewer must open or preview the post for execution in that viewer's browser context.

The record

CVE
CVE-2023-3746
Published
Oct 16, 2023
Updated
Apr 23, 2025
Vendor
Automattic
Product
ActivityPub
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 16, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Automattic · ActivityPubversion=0 <1.0.0

Published CVSS scores

5.4NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
5.4CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

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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