Stored XSS via Quote Bypass in Grav CMS

Grav before 2.0.15 contains a stored cross-site scripting vulnerability in the detectXss() function where unpaired quotes in unquoted attribute values bypass event-handler detection. Authenticated editors can inject event handlers like onerror= that pass validation and execute in visitor browsers when page content is rendered.

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

Grav CMS versions before 2.0.15 contain a stored cross-site scripting vulnerability where the detectXss() validation function fails to properly handle unpaired quotes in unquoted HTML attribute values. This allows authenticated editors to inject malicious event handlers (such as onerror=) that bypass security checks and persist in page content. When visitors render the compromised pages, the injected handlers execute in their browsers with the visitor's privileges, enabling attackers to steal credentials, hijack sessions, or deliver malware. Any organization running Grav as a content management system with multiple editors is at risk, particularly those where editor accounts may be compromised or insider threats exist.

Casky's 322 mapped skills leverage Claude's extended reasoning to detect the attack patterns underlying this vulnerability across MITRE ATT&CK techniques TA0001 (Initial Access) and TA0043 (Reconnaissance). Practitioners using Casky would identify suspicious patterns including: attempts to inject HTML event handlers through content fields, validation bypass attempts using quote manipulation, and stored payloads designed to execute on page render. The platform's skills would flag deviations from legitimate editor behavior—such as unusual attribute syntax, event handler usage in page metadata, or content modifications that introduce client-side execution contexts. Security teams would see detailed findings linking these indicators to CWE-79 (Improper Neutralization of Input During Web Page Generation) and receive context-aware detection that distinguishes between benign editor activity and exploitation attempts.

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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-2026-75828.

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-2026-75828

Casky has 322 skills that investigate the attack patterns behind CVE-2026-75828. Run one and get CVSS-scored findings in 3 minutes.

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