Webmention <= 5.8.0 - Unauthenticated Stored Cross-Site Scripting via MF2 'photo'/'url' Author Properties
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.
Summary
The Webmention plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to and including 5.8.0 via parser-derived 'avatar' and 'url' author metadata. This is due to insufficient input sanitization and output escaping on user-supplied MF2 author properties processed by the unauthenticated webmention REST endpoint and rendered directly into HTML 'value' attributes by the edit-comment-form template without esc_attr() or esc_url(). This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a privileged user (moderator or administrator) opens the affected comment edit screen.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2026-10513
- 2026-10-03 Alias added: GHSA-q4c4-6mqr-j8hq
References
Other 4
- https://www.wordfence.com/threat-intel/vulnerabilities/id/5a4e144a-3c84-4da3-8fa6-e5fe9c897efe?source=cve
- https://plugins.trac.wordpress.org/browser/webmention/tags/5.7.0/templates/edit-comment-form.php#L15
- https://plugins.trac.wordpress.org/browser/webmention/tags/5.7.0/includes/handler/class-mf2.php#L129
- https://plugins.trac.wordpress.org/changeset/3583033/webmention
More pfefferle vulnerabilities
- TI-2026-00478 Webmention <= 5.6.2 - Unauthenticated Blind Server-Side Request Forgery CVSS 3.1HIGH 7.2
- TI-2026-00480 Webmention <= 5.6.2 - Authenticated (Subscriber+) Server-Side Request Forgery CVSS 3.1MEDIUM 6.4
- TI-2026-83489 Stored cross-site scripting in Webmention plugin for WordPress CVSS 3.1MEDIUM 6.1
Sources
- CVE-2026-10513 · CVE Program
- CVE-2026-10513 · NVD
- FIRST EPSS
- GHSA-q4c4-6mqr-j8hq · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences