WordPress Quill Forms Plugin Stored XSS Injection Flaw

The Quill Forms | Conversational Multi Step Forms, Surveys & quizzes plugin for WordPress is vulnerable to Stored Cross-Site Scripting in all versions up to, and including, 5.7.1 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.

Casky was already ahead

This CVE exploits attack patterns that Casky's 322matched 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 Quill Forms plugin for WordPress contains a stored cross-site scripting (XSS) vulnerability affecting all versions through 5.7.1. This flaw stems from insufficient input sanitization and output escaping in form processing, allowing unauthenticated attackers to inject malicious JavaScript directly into pages. When legitimate users access these compromised pages, the injected scripts execute in their browsers with the privileges of the page context, potentially leading to credential theft, session hijacking, malware distribution, or defacement. Any WordPress site running this popular forms and surveys plugin is at risk, with no authentication required to exploit this vulnerability.

Casky.ai maps this vulnerability to 322 security skills that help practitioners detect the attack patterns behind CVE-2026-75091. The underlying techniques (TA0001: Initial Access and TA0043: Reconnaissance) reveal how attackers probe for unprotected input fields and inject payloads. Using Claude AI with extended reasoning, practitioners gain visibility into two critical detection vectors: first, identifying CWE-79 patterns by analyzing form submissions for script tags, event handlers, and encoded payloads that bypass weak sanitization; second, detecting post-injection behavior when stored XSS executes during page loads, manifesting as unexpected DOM modifications or credential exfiltration requests. Security teams using Casky would see findings highlighting suspicious form data patterns, unusual JavaScript execution contexts, and anomalous user session behavior—enabling rapid remediation before widespread compromise.

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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 →

322 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-75091.

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-2026-75091

Casky has 322 skills that investigate the attack patterns behind CVE-2026-75091. Run one and get CVSS-scored findings in 3 minutes.

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