The OTP Login & Register Woocommerce plugin for WordPress is vulnerable to Authentication Bypass via OTP Brute Force in all versions up to, and including, 2.7.2

Overview

The OTP Login & Register Woocommerce plugin for WordPress is vulnerable to Authentication Bypass via OTP Brute Force in all versions up to, and including, 2.7.2. The vulnerability exists because the OTP rate-limit attempt counter in process_otp_form is keyed exclusively on the attacker-controlled xoo_ml_user_ip_data cookie's ip_address field, allowing unlimited counter resets by simply rotating the cookie, while the OTP itself is generated with PHP's non-cryptographic rand() function over a default space of only 9,000 possible values (1000–9999), and both the OTP issuance endpoint (xoo_ml_login_with_otp) and verification endpoint (xoo_ml_otp_form_submit) are registered as unauthenticated wp_ajax_nopriv actions with no nonce or capability checks. This makes it possible for unauthenticated attackers to brute-force the OTP for any registered account and obtain a full WordPress authentication session — including for administrator accounts — via wp_set_auth_cookie() in login_user_with_otp(). Exploitation requires the attacker to know the target user's registered phone number, which is used to trigger OTP issuance via the unauthenticated xoo_ml_login_with_otp endpoint.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.