EUVD-2026-39019Severity by source
AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
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).
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.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. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the attacker control a maliciously customized ActivityPub server and that the victim Ghost instance (prior to 3.1.0) federate with or consume posts from that server - federation must be enabled and the victim must follow/receive the attacker's content. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score is 7.5 (High) with vector AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker stands up or customizes an ActivityPub server and crafts a post containing embedded JavaScript, then ensures a victim Ghost instance federates with or follows that server. When a Ghost user opens or views the shared malicious post in the ActivityPub client, the injected script runs in their authenticated browser session, potentially exfiltrating session tokens or performing actions as that user. … |
| Remediation | 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. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
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. …
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External POC / Exploit Code
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