YMC Filter CVE-2026-16559

Exploitation requires the attacker to control a WordPress account with at least the Author role - typically granted to content contributors - making external unauthenticated exploitation impossible. The YMC Filter plugin must be installed, active, and unpatched (version below 3.12.9), and its icon upload feature must be reachable by Author-role users (default plugin behavior). A victim holding any WordPress role, including Administrator, must then navigate to or preview the uploaded SVG file, providing the required user interaction. Exploitation is bounded by: (1) need for an Author-or-above account on the target site, (2) YMC Filter plugin present and unpatched, and (3) at least one other user viewing the malicious SVG. The attack is network-accessible but not exploitable by unauthenticated or anonymous actors.

The provided CVSS vector (AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:H) contains two material inconsistencies worth flagging. First, PR:H (high privileges required) conflicts with the description's explicit characterization of the Author role as 'low-privileged' - in WordPress's role hierarchy, Author sits well below Editor and Administrator. Second, S:U (Unchanged scope) is inconsistent with stored XSS, where impact is realized in a distinct user's browser session rather than the attacker's own context; S:C (Changed) is technically more appropriate per CVSS guidance. C:H/I:H/A:H with S:U further overstates impact relative to what browser-resident script execution can achieve without direct server access. Correcting for these, actual risk is moderate: the attack requires an authenticated Author account and victim interaction, and the EPSS score of 0.15% confirms no observed automated exploitation. However, a public POC from WPScan and the relatively accessible authentication barrier make this a credible insider or compromised-account pivot threat. No CISA KEV listing - this is not confirmed actively exploited.

An attacker holding a WordPress Author account - obtained via registration, credential stuffing, or a compromised contributor - crafts an SVG file embedding a JavaScript payload that exfiltrates document.cookie to an attacker-controlled endpoint and uploads it using YMC Filter's icon upload feature. When a site administrator reviews or previews the uploaded icon, the script silently executes in their browser at the site's origin, capturing the admin session token. A public POC documented by WPScan makes this attack reproducible by low-skill actors.