WordPress Cache Plugin Stored XSS via HTTP Host Header

The WP Fastest Cache – WordPress Cache Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via HTTP Host Header in all versions up to, and including, 1.5.0 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. This requires the Polylang or Polylang Pro plugin to be active and the Combine JS option to be enabled, as these conditions trigger the vulnerable Host-header-to-URL code path that writes attacker-controlled script src values into the shared page-cache file served to all subsequent visitors.

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

WP Fastest Cache versions up to 1.5.0 contain a stored cross-site scripting (XSS) vulnerability exploitable through the HTTP Host Header when Polylang and the Combine JS option are active. Unauthenticated attackers can inject malicious scripts that persist in cached pages, executing whenever users access affected content. This vulnerability matters because WordPress sites rely heavily on caching plugins for performance, and the stored nature means the payload affects all subsequent visitors—not just the attacker's session. Affected organizations include any WordPress deployment running the vulnerable plugin with the specific Polylang configuration, making this a broad-reaching threat to small businesses, enterprises, and content publishers.

Casky's 323 mapped skills detect the attack patterns behind CVE-2026-19760 by correlating MITRE ATT&CK techniques TA0001 (Reconnaissance) and TA0043 (Reconnaissance) with CWE-79 (Improper Neutralization of Input During Web Page Generation). Claude's extended reasoning capabilities identify HTTP Host Header injection attempts during the initial reconnaissance phase, then track how unsanitized input flows through cache generation systems. Practitioners using Casky would see findings highlighting: suspicious Host Header values in web logs, anomalous cache file contents containing script tags, and execution patterns indicating XSS payloads. The platform correlates these signals across your security stack to distinguish legitimate traffic from reconnaissance probing and cache poisoning attempts, enabling teams to patch before exploitation scales across their user base.

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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-2026-19760.

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-2026-19760

Casky has 323 skills that investigate the attack patterns behind CVE-2026-19760. Run one and get CVSS-scored findings in 3 minutes.

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