Vulnerabilities in pkg:npm/@tryghost/activitypub

PACKAGE
Advisory Identifier: GHSA-xpp7-93x6-v29m
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Advisory Summary

CVE-2026-53950 is a HIGH (CVSS 7.5) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting @tryghost/activitypub libraries in the npm ecosystem. The issue involves xss in ghost's activitypub client. Remediation is available by upgrading affected packages to version 3.1.0.

1 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:npm/@tryghost/activitypub

1 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:npm/@tryghost/activitypub. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-xpp7-93x6-v29m CVE-2026-53950 HIGH XSS in Ghost's ActivityPub client

CVE-2026-53950 at a Glance

CVE Identifier CVE-2026-53950
GHSA Identifier GHSA-xpp7-93x6-v29m
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product @tryghost/activitypub
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-53950

To remediate this vulnerability, upgrade all affected @tryghost/activitypub dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@tryghost/activitypub fixed: 3.1.0 
npm install @tryghost/activitypub@3.1.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @tryghost/activitypub

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-53950, inspect your project dependencies using npm:

npm ls @tryghost/activitypub

Analyze the terminal output to locate any version of @tryghost/activitypub in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.1.0), your application is affected.

Note: The npm ls @tryghost/activitypub command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In @tryghost/activitypub, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact The ActivityPub client in Ghost was vulnerable to JavaScript injection on posts shared by a maliciously customised ActivityPub server. ### Vulnerable Versions This vulnerability is present in the @tryghost/activitypub package up to v3.0.8. All prior versions are also affected. ### Patches @tryghost/activitypub v3.1.0 contains a fix for this issue and is also automatically fetched by Ghost. ### References Ghost thanks Brad Geesaman, Ghost Security for disclosing this vulnerability responsibly. ### For more information If you have any questions or comments about this advisory, email Ghost at [security@ghost.org](mailto:security@ghost.org).

CVE-2026-53950 Affected @tryghost/activitypub Versions

1 component(s)
Fixed Versions:
3.1.0
Product / Package Ecosystem Affected Versions Fixed Version
@tryghost/activitypub
npm/@tryghost/activitypub
npm
< 3.1.0
3.1.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/TryGhost/Ghost/security/advisories/GHSA-xpp7-93x6-v29m
NVD — CVE-2026-53950 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-53950
@tryghost/activitypub Source Repository REPOSITORY
https://github.com/TryGhost/Ghost

Frequently Asked Questions

What is CVE-2026-53950?
CVE-2026-53950 is a security vulnerability in @tryghost/activitypub involving XSS in Ghost's ActivityPub client under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which @tryghost/activitypub versions are affected?
Affected versions include releases prior to 3.1.0 across affected packages: @tryghost/activitypub.
What version fixes CVE-2026-53950?
Upgrading to 3.1.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @tryghost/activitypub affected?
Yes, @tryghost/activitypub is affected in releases prior to 3.1.0. Upgrade your dependency to 3.1.0 or later.
What is the CVSS score of CVE-2026-53950?
CVE-2026-53950 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-53950?
CVE-2026-53950 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check npm dependencies for CVE-2026-53950?
Run the dependency tree command: 'npm ls @tryghost/activitypub'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xpp7-93x6-v29m",
  "modified" : "2026-08-04T21:54:01Z",
  "published" : "2026-08-04T21:54:01Z",
  "aliases" : [ "CVE-2026-53950" ],
  "summary" : "XSS in Ghost's ActivityPub client",
  "details" : "### Impact\n\nThe ActivityPub client in Ghost was vulnerable to JavaScript injection on posts shared by a maliciously customised ActivityPub server.\n\n### Vulnerable Versions\n\nThis vulnerability is present in the @tryghost/activitypub package up to v3.0.8. All prior versions are also affected. \n\n### Patches\n\n@tryghost/activitypub v3.1.0 contains a fix for this issue and is also automatically fetched by Ghost.\n\n### References\n\nGhost thanks Brad Geesaman, Ghost Security for disclosing this vulnerability responsibly. \n\n### For more information\n\nIf you have any questions or comments about this advisory, email Ghost at [security@ghost.org](mailto:security@ghost.org).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@tryghost/activitypub"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/TryGhost/Ghost/security/advisories/GHSA-xpp7-93x6-v29m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-53950"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/TryGhost/Ghost"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-04T21:54:01Z",
    "nvd_published_at" : "2026-06-24T19:17:12Z"
  }
}