Kubio AI Page Builder Stored XSS in Unauthenticated Submissions

The Kubio AI Page Builder WordPress plugin before 2.9.3 does not limit its widening of the allowed HTML elements to the editor context, so the wider set is applied when filtering content submitted by unauthenticated users as well, allowing them to store markup which the Kubio AI Page Builder WordPress plugin before 2.9.3's own script later executes in the browser of any visitor, or of an administrator reviewing the still-unapproved submission.

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 Kubio AI Page Builder WordPress plugin before version 2.9.3 contains a stored cross-site scripting (XSS) vulnerability that allows unauthenticated attackers to inject malicious HTML and JavaScript into the application. The flaw stems from overly permissive HTML element filtering that was intended only for the editor context but is incorrectly applied to user-submitted content from unauthenticated sources. Once stored, the malicious payload executes in the browsers of any site visitor or administrator reviewing pending submissions, making this a high-impact supply chain risk for WordPress sites using this popular page builder plugin.

Casky's 323 mapped security skills detect this vulnerability pattern by analyzing initial access and execution techniques (TA0001 and TA0043). When practitioners run Casky's extended reasoning analysis, they would identify: (1) CWE-79 patterns indicating improper input validation in HTML filtering logic; (2) anomalous submission payloads containing script tags or event handlers that bypass sanitization; (3) stored content artifacts that execute client-side code; and (4) behavioral indicators of administrator accounts interacting with malicious submissions. Practitioners would see findings highlighting the attack chain—from unauthenticated submission ingestion through to arbitrary code execution in victim browsers—with specific skill recommendations for input validation hardening, output encoding enforcement, and Content Security Policy implementation across their WordPress infrastructure.

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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-2026-88783.

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-2026-88783

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