CVE-2026-111109: Webmention stored cross-site scripting (XSS) vulnerability
medium 6.1 published 2026-10-31 · updated 2026-11-02
- Affected versions
- 5.10.1 and older
- Fixed in
- 5.10.2 *
- Latest version
- 5.11.0
- Severity
- Medium · CVSS 6.1
- Active installs
- 900+
- Type
- Stored cross-site scripting (XSS)
* The source does not name a fixed version; this is the first wordpress.org release after the last affected version.
What an attacker needs
- Access: None. No account or login is needed.
- Interaction: It also needs someone on the site (often an admin) to click a link, open a page or submit a form the attacker prepared.
CVSS vector (score by Wordfence): CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
What to do now
- Update Webmention to 5.10.2 or newer (the latest is 5.11.0): Dashboard → Updates, or Plugins → “update now”.
- If you cannot update right away, deactivate it until you can.
- Turn on auto-updates for it: Plugins → “Enable auto-updates” on its row.
- Not sure which version you run? Check your version against every known Webmention issue.
With WP-CLI:
wp plugin get webmention --field=version. - If you ran an affected version and something looks off (new admin users, spam pages, redirects), run the free scan below.
The advisory
The Webmention plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Open Graph og:title meta tag of a webmention source URL in versions up to, and including, 5.10.1. This is due to insufficient input sanitization: Meta::add_properties() maps og:title to the Item::name property, but Item has no concrete set_name() method, so Item::__call() stores the value raw while sibling set_content()/set_summary() paths route through webmention_sanitize_html(); Item::get_content() then falls back to the raw name when content and summary are empty, and Receiver::process() explicitly removes the core wp_filter_kses / wp_filter_post_kses hooks on pre_comment_content before calling wp_new_comment(), so the payload is persisted to comment_content as-is. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page, after an administrator approves the resulting pending webmention comment. Successful exploitation additionally requires an action by an administrator — the attacker cannot trigger the vulnerability on their own.
References
- NVD CVE-2026-111109 nvd.nist.gov
- Wordfence advisory www.wordfence.com
- github.com github.com
- Plugin source plugins.trac.wordpress.org
Related
Ran an affected version? Check your site for signs of a hack
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Where this data comes from
- CVE record, score and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
- Versions and install counts: wordpress.org/plugins/webmention (Plugins API), fetched 2026-11-04.
- The summary, “what an attacker needs” and “what to do” sections are our plain-English reading of the record and the plugin's release history; the quoted description is the record's own text. Spot an error? Email Daniel.