WebAuthn Passkey Registration Bypass in phpMyFAQ

phpMyFAQ 4.0.0 before 4.1.9 contains an authentication bypass vulnerability where WebAuthn registration endpoints attach credentials to any account without authentication or challenge validation. Attackers can stage a victim username, submit a forged fmt=none attestation to register a passkey, then log in bypassing passwords and TOTP for account takeover.

Casky was already ahead

This CVE exploits attack patterns that Casky's 283matched 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

phpMyFAQ 4.0.0 through 4.1.8 contains a critical authentication bypass vulnerability in its WebAuthn implementation. The vulnerability allows attackers to register passkeys to arbitrary accounts without proper authentication or challenge validation. By exploiting the fmt=none attestation format, an attacker can stage a victim's username and register a forged credential, subsequently gaining account access without knowledge of the password or TOTP codes. This affects organizations running vulnerable phpMyFAQ versions that rely on the platform for FAQ management and user authentication, potentially exposing administrative accounts and sensitive information to complete account takeover.

Casky's 283 mapped skills across MITRE ATT&CK's Initial Access (TA0004) and Credential Access (TA0006) tactics detect the attack patterns embedded in this vulnerability. Practitioners using Casky would observe findings related to credential manipulation without multi-factor enforcement (CWE-287), detection of improperly validated WebAuthn challenge-response sequences, and lateral movement indicators following successful passkey registration to high-privilege accounts. Claude's extended reasoning capabilities correlate suspicious registration patterns—such as fmt=none attestations lacking proper verification—with subsequent authentication events using newly registered credentials, surfacing the account takeover chain that would otherwise appear as legitimate login activity in standard logs.

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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 →

283 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-111911.

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

Access with Stolen Session Cookie

identity access management · low

Run

MITRE ATT&CK Techniques

TA0004 TA0006

Investigate the attack patterns behind CVE-2026-111911

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