Themify Builder Stored XSS via CSS Fonts Parameter

The Themify Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'css[fonts]' Parameter in all versions up to, and including, 7.8.1 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The nonce required to reach the vulnerable endpoint is embedded in plain sight within the front-end page markup for all visitors, reducing the access control to a CSRF token rather than an authentication barrier and making the endpoint fully exploitable by unauthenticated attackers.

Casky was already ahead

This CVE exploits attack patterns that Casky's 323matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

The Themify Builder plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability in versions up to 7.8.1 that allows unauthenticated attackers to inject malicious scripts through the 'css[fonts]' parameter. Due to insufficient input sanitization and output escaping, these injected scripts persist in the database and execute whenever any user accesses the affected page. This vulnerability is particularly dangerous because the nonce token required to exploit it is exposed in plain HTML markup visible to all visitors, effectively eliminating a critical protection mechanism. WordPress site administrators using Themify Builder are at immediate risk, as attackers can deface content, steal credentials, redirect users, or perform actions on behalf of legitimate visitors without requiring authentication.

Casky's 323 matching security skills leverage Claude AI with extended reasoning to detect the attack patterns underlying this vulnerability by mapping to MITRE ATT&CK techniques TA0001 (Reconnaissance) and TA0043 (Reconnaissance). Practitioners using Casky would identify suspicious patterns such as: unusual POST requests to plugin endpoints with manipulated 'css' parameters containing script tags or event handlers; repeated attempts to inject payloads with varying encoding schemes to bypass filters; and patterns consistent with CWE-79 violations where user input flows directly into stored output without proper escaping. The platform's skill-based detection would flag requests combining exposed nonce tokens with malicious CSS font declarations, helping teams distinguish between legitimate Themify Builder customizations and exploitation attempts, enabling faster incident response and vulnerability remediation.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

323 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-95864.

Abuse of Public-Facing API: Mobile API Abuse

mobile security · low

Run

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

MITRE ATT&CK Techniques

TA0001 TA0043

Investigate the attack patterns behind CVE-2026-95864

Casky has 323 skills that investigate the attack patterns behind CVE-2026-95864. Run one and get CVSS-scored findings in 3 minutes.

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