What is the CVSS score of CVE-2026-53950?

CVE-2026-53950 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.2%.

Which versions of Ghost are affected by CVE-2026-53950?

Ghost installations running ActivityPub federation are vulnerable to a HIGH-severity cross-site scripting (XSS) attack where malicious federated servers can inject code that executes in the browser…. A patch is available.

Is there a public PoC exploit available for CVE-2026-53950?

Yes, a public proof-of-concept exploit is available for CVE-2026-53950. Prioritise patching immediately. EPSS: 0.2%.

How to fix or mitigate CVE-2026-53950?

Within 24 hours: Inventory all Ghost deployments and identify which have @tryghost/activitypub enabled (versions prior to 3.1.0) and document connected federated servers. Within 7 days: Disable ActivityPub federation on non-critical instances or restrict federation to explicitly trusted servers only; implement strict Content Security Policy headers to prevent inline script execution. Within 30 days: Monitor Ghost security advisories and vendor releases for availability of @tryghost/activitypub version 3.1.0 or later; test and deploy patch immediately upon release.

Ghost CVE-2026-53950

EUVD-2026-39019 HIGH

Cross-site Scripting (XSS) (CWE-79)

2026-06-24 GitHub_M

GHSA-xpp7-93x6-v29m

XSS Ghost

7.5

CVSS 3.1 · Vendor: GitHub_M

Severity by source

Vendor (GitHub_M) PRIMARY

7.5 HIGH

AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

vuln.today AI

6.9 MEDIUM

Network-delivered via federation (AV:N) but needs an attacker-run malicious server plus victim viewing (AC:H, UI:R); script escapes into the user's browser session (S:C, C:H), limited integrity impact and no real availability loss (A:N).

3.1 AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N

4.0 AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch available

Jun 24, 2026 - 20:03 EUVD

Analysis Generated

Jun 24, 2026 - 19:17 vuln.today

DescriptionCVE.org

@tryghost/activitypub is Ghost’s social/federation client app. Prior to 3.1.0, the ActivityPub client in Ghost was vulnerable to JavaScript injection on posts shared by a maliciously customised ActivityPub server. This vulnerability is fixed in 3.1.0.

AnalysisAI

Cross-site scripting (JavaScript injection) in Ghost's ActivityPub client (@tryghost/activitypub) prior to version 3.1.0 allows a malicious federated server to embed attacker-controlled script in shared posts that executes in the browser of a victim Ghost user who views the content. The flaw stems from improper sanitization of post content received over ActivityPub federation, enabling session theft or actions performed in the victim's authenticated context. There is no public exploit identified at the time of analysis, and the issue is not listed in CISA KEV.

Technical ContextAI

The affected component is @tryghost/activitypub, the social/federation client bundled with the Ghost publishing platform, which implements the ActivityPub protocol to consume and display posts from remote (federated) servers. The root cause is CWE-79 (Improper Neutralization of Input During Web Page Generation / Cross-site Scripting): content fields delivered in ActivityPub objects from a remote actor are rendered into the Ghost client UI without adequate output encoding or HTML sanitization, so a remote server operator who customizes the ActivityPub responses can smuggle active JavaScript into the rendered post. The single CPE provided, cpe:2.3:a:tryghost:ghost:*, identifies the Ghost application generically; because federation inherently means processing untrusted data from servers outside the operator's control, any sanitization gap in the rendering path becomes directly attacker-influenceable.

RemediationAI

Upgrade the Ghost ActivityPub client (@tryghost/activitypub) to version 3.1.0 or later, which contains the fix; this is the primary and recommended remediation per the vendor advisory at https://github.com/TryGhost/Ghost/security/advisories/GHSA-xpp7-93x6-v29m. If immediate upgrade is not possible, reduce exposure by limiting or disabling ActivityPub federation, or by restricting which remote servers your instance federates with so content is only consumed from trusted sources - the trade-off is loss of social/federation functionality and reach. Additionally, deploying a restrictive Content-Security-Policy that disallows inline script execution in the Ghost client context can blunt injected JavaScript, though CSP is a defense-in-depth measure and may break legitimate inline scripts or themes and is not a substitute for the patch. Exact fix version: 3.1.0 (vendor-released patch).