---
id: "CVE-2026-111109"
kind: "vulnerability"
aliases: ["CVE-2026-111109"]
title: "WordPress Webmention plugin: unsanitized og:title enables stored cross-site scripting"
severity: "medium"
cvss: 6.1
epss: 0.0028
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "self-hosted", "webmention", "wordpress"]
not_affected_if: ["newer-version-installed", "webmention-plugin-absent"]
published_at: "2026-10-31T07:16:34+00:00"
first_seen_at: "2026-10-31T07:34:07+00:00"
updated_at: "2026-10-31T18:03:03+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-111109", "first_seen_at": "2026-10-31T07:34:07+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-111109", "first_seen_at": "2026-10-31T18:03:03+00:00"}]
---

# WordPress Webmention plugin: unsanitized og:title enables stored cross-site scripting

The Webmention plugin for WordPress up to and including 5.10.1 stores the Open Graph og:title value from a webmention source URL without sanitizing it, and removes WordPress's usual comment filters before saving. An unauthenticated attacker can get a script saved into a comment that runs in the browser of anyone who views the page after an administrator approves it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Webmention plugin version in the WordPress admin plugin list or with `wp plugin get webmention --field=version`
- Look for pending webmention comments that contain script tags or unusual og:title text under the comment moderation queue

## Fix

- Webmention plugin: upgrade to a version later than `5.10.1` (the fixed version is not stated in the sources)

## Timeline

- 2026-10-31T07:34:07+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-111109
- 2026-10-31T18:03:03+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-111109

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_