WordPress AMP Plugin Stored XSS via Comment Sanitization

The AMP for WP – Accelerated Mobile Pages plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Comment Content via Regex Transformation in all versions up to, and including, 1.1.16 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 crafted payload uses only WordPress-permitted comment tags and attributes (an anchor with href and title), and the AMP sanitizer pipeline omits javascript: protocol blocking, meaning neither the comment save filter nor the AMP output stage removes the malicious URI introduced by the transformation.

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 AMP for WP plugin contains a stored cross-site scripting (XSS) vulnerability in its comment processing functionality, allowing unauthenticated attackers to inject malicious scripts that persist in page content. The vulnerability stems from insufficient input sanitization and output escaping when the plugin applies regex transformations to comment data. Because comments are visible to all site visitors, attackers can execute arbitrary JavaScript in users' browsers—potentially stealing sessions, credentials, or redirecting users to malicious sites. This affects any WordPress installation running the vulnerable plugin versions up to 1.1.16, making it a broad-impact threat to the WordPress ecosystem.

Casky's 323 matched skills leverage Claude's extended reasoning to detect the attack patterns underlying this vulnerability by mapping it across MITRE ATT&CK's Initial Access (TA0001) and Reconnaissance (TA0043) techniques. Practitioners using Casky would observe detection signals including: anomalous comment content containing script tags or event handlers that bypass WordPress sanitization filters; regex patterns that manipulate HTML entity encoding to evade escaping mechanisms; and payloads crafted to exploit the gap between input validation and output rendering. The platform would flag suspicious comment submissions with event attributes (onclick, onload, etc.) and data URIs that WordPress normally permits in specific contexts but the plugin fails to sanitize—enabling practitioners to identify compromise attempts before malicious scripts reach production pages.

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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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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-2026-83591.

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

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