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

• Severity: medium (CVSS 6.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-17 · updated 2026-10-19
• Weakness: CWE-79

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.

Affected products

• wssoffice21 YMC Filter: through 3.12.19

References

• 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/abstracts/FG_REST_Abstract_Controller.php#L66
• 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://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/3.12.20/ymc2/src/api/controllers/frontend/FG_REST_Frontend_Search_Controller.php
• https://wordpress.org/plugins/ymc-smart-filter
• https://www.wordfence.com/threat-intel/vulnerabilities/id/27cfa62d-ba16-4344-be0c-82cac4d21d1c?source=cve

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