WordPress Plugin Stored XSS via Base64-Encoded Redirect URLs

The No External Links plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Log URL via /goto/{base64} Redirect in all versions up to, and including, 5.2.0 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 is only exploitable when the administrator has enabled the 'Link Encoding: Base64' option in the plugin settings.

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 No External Links WordPress plugin contains a stored cross-site scripting (XSS) vulnerability in its redirect functionality when Base64 link encoding is enabled. Attackers can inject malicious JavaScript through the /goto/{base64} endpoint by crafting specially formatted base64-encoded payloads that bypass insufficient input sanitization. When site visitors click these injected links, the malicious scripts execute in their browsers with full context of the WordPress site, potentially stealing credentials, session tokens, or performing unauthorized actions. This affects all WordPress installations running the plugin up to version 5.2.0 where administrators have enabled Base64 encoding, making it a supply-chain risk for any site using this popular plugin.

Casky's 323 matching skills detect this attack pattern by mapping to MITRE ATT&CK techniques TA0001 (Initial Access) and TA0043 (Reconnaissance). Claude's extended reasoning analyzes CWE-79 (Improper Neutralization of Input During Web Page Generation) by identifying the control flow where unsanitized base64 input reaches output without proper HTML entity encoding. Practitioners using Casky would observe findings highlighting: (1) insufficient input validation on the /goto/ redirect handler, (2) lack of output escaping when rendering decoded URLs, and (3) the attack chain showing how unauthenticated threat actors inject persistent payloads that trigger on user interaction. The skills framework would recommend input validation against whitelist patterns, output encoding via WordPress escaping functions (esc_url, wp_kses), and content security policy headers to mitigate execution of injected scripts.

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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-2026-95670.

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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